When did the Cretaceous period begin?
Jurassic Museum of Asturias
In the hall representing the Cretaceous period, which is the last period of the Mesozoic era from 145 to 66 million years ago, the displays relate to the biological and social habits of dinosaurs, reasons for their extinction by the end of the Cretaceous period, that are attributed to meteorite, volcanic eruptions and intense geographic and climatic changes. Evolution of birds inferred as theropods evolving from the non-avian dinosaurs are represented by the "Archaeopteryx" (a prehistoric bird) and dinosaurs such as the "Deinonychus" or the "Dromaeosaurus".
Helladic chronology
Helladic society and culture have antecedents in Neolithic Greece when most settlements were small villages which subsisted by means of agriculture, farming and hunting. The gradual development of skills such as bronze metallurgy, monumental architecture and construction of fortifications brought about the transition from the Neolithic to the Bronze Age. The Late Helladic (c.1550–c.1050) is sometimes called the Mycenaean Age because Mycenae was then the dominant state in Greece. At the end of the Bronze Age (c.1050 BC), Aegean culture went into a long period of decline, termed a Dark Age by some historians, as a result of invasion and war.
Geology of the southern North Sea
This phase is currently active today and started in the Cretaceous.In the late Cretaceous and in the Tertiary inversion phases in the Southern North Sea region occurred due to the Alpine orogeny and its compressional stresses. Since there had been inversion the Zechstein salt played a huge role by acting as a buffer between two structural regimes. Although the phase reactivated pre-existing faults it allowed the salt tectonics to remain active during the Tertiary as the sediments were deposited, and later became penetrated by the salt diapers. The Alpine phase did add more structural confusion to the geologic history, but it also help create more traps with the Zechstein salt.
Prehistory of the United States
Near the end of the Cretaceous, the Western Interior Seaway began to withdraw. This regression would end up resulting in both halves of North America reuniting. As the seaway withdrew a coastal plain expanded southward into the northern part of the western interior. Powerful geologic forces began to fold and distort the rocks of Idaho, Utah, and Wyoming, beginning the processes that would form the Rocky Mountains. Rivers flowing across the eastern part of what is now Montana, deposited the sediments now known as the Hell Creek Formation. At the time, Montana was home to some of the most famous dinosaurs; creatures like "Edmontosaurus", "Pachycephalosaurus", "Triceratops", and "Tyrannosaurus". Despite the western upheaval, the eastern US had achieved geological stability by the Late Cretaceous. The weather was uniformly warm and rainy throughout the year. Flowering plants were now common and fossil of broadleaf trees and shrubs were preserved in Late Cretaceous rocks.
Berriasian
In the geological timescale, the Berriasian is an age or stage of the Early Cretaceous. It is the oldest, or lowest, subdivision in the entire Cretaceous. It spanned the time between 145.0 ± 4.0 Ma and 139.8 ± 3.0 Ma (million years ago). The Berriasian succeeds the Tithonian (part of the Jurassic) and precedes the Valanginian.
Geology of Scotland
In the Cretaceous (145–66 Ma), Laurasia split into the continents of North America and Eurasia. Sea levels rose globally during this period and much of low-lying Scotland was covered in a layer of chalk. Although large deposits of Cretaceous rocks were laid down over Scotland, these have not survived erosion except in a few places on the west coast such as Loch Aline in Morvern where they form a part of the Inner Hebrides Group. At the end of this period the Cretaceous–Paleogene extinction event brought the age of dinosaurs to a close.
Tectonic evolution of the Transantarctic Mountains
Breakup of the super-continent Gondwana started in the early Jurassic around 184 million years ago (Ma), but Antarctica did not break up from Australia until the late Cretaceous (80 Ma). Just before the breakaway in the Late Jurassic and Early Cretaceous, rifting began to occur near the soon-to-be Transantarctic Mountains. It is uncertain whether this first episode of rifting caused any uplift of the mountain range. Some researchers say this episode is a reactivation of rift that was formed during the Gondwanide Orogeny, but it has never been proven. This event was followed by low-angle extensional faulting along the East Antarctic plate. No uplift occurred during this initial phase of faulting due to counteracting erosional events. Shortly after, during the Mid Cretaceous (100 Ma), the West Antarctic Rift began to form. Certain models show that the rapid rifting and intense thermal forces are due to a shallow (50 km depth) lithosphere-asthenosphere boundary under the Transantarctic Mountains. Rifting in this area is still going on today. Such a long period of rifting leads to uplift due to prolonged lateral heat conduction in the mountain belt. This is backed by seismic evidence. Initial surface uplift began approximately 55 Ma during the Early Cenozoic era.
Dakota Formation
Beginning in the Early Cretaceous, the Cretaceous Seaway spread south from what is now the Arctic Ocean and connected with a short northward extension from the Gulf of Mexico. This marine transgression of the ocean onto what was formerly land, was completed by the late Albian (~100 MA) thereby dividing North America in half. On the eastern side of the Seaway, sediments that would become the Dakota Formation were deposited as coastal and nearshore marine sands and silts. As the seaway continued to deepen and widen, this eastern shoreline moved progressively eastward throughout the Cenomanian. Meanwhile, on the western side of the seaway, sediments were carried eastwards and northeastwards by rivers from mountains located along what is the Nevada-Utah border.
Geological history of Earth
During the Cretaceous, the late Paleozoic-early Mesozoic supercontinent of Pangaea completed its breakup into present day continents, although their positions were substantially different at the time. As the Atlantic Ocean widened, the convergent-margin 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. Though Gondwana was still intact in the beginning of the Cretaceous, Gondwana itself broke up as South America, Antarctica and Australia rifted away from Africa (though India and Madagascar remained attached to each other); 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.
Paleocene
The Paleocene Epoch is bracketed by two major events in Earth's history. It started with the mass extinction event at the end of the Cretaceous, known as the Cretaceous–Paleogene (K–Pg) boundary. This was a time marked by the demise of non-avian dinosaurs, giant marine reptiles and much other fauna and flora. The die-off of the dinosaurs left unfilled ecological niches worldwide. The Paleocene ended with the Paleocene–Eocene Thermal Maximum, a geologically brief (~0.2 million year) interval characterized by extreme changes in climate and carbon cycling.
Pleistocene
The Pleistocene is the first epoch of the Quaternary Period or sixth epoch of the Cenozoic Era. In the ICS timescale, the Pleistocene is divided into four stages or ages, the Gelasian, Calabrian, Middle Pleistocene (unofficially the 'Chibanian') and Upper Pleistocene (unofficially the 'Tarantian'). In addition to this international subdivision, various regional subdivisions are often used.
Herrera Period
Agriculture started around 5000 years before present which led to the development of more complex societies, of which the Herrera Period is one of many in the Andean civilizations. Early evidence of inhabitation has been found in Zipacón and is dated at 3270 BCE. From the Herrera Period ceramic has been found. The oldest ceramic evidence found dates to 2500 BP (500 BCE), except for one piece found near Tocarema and dated at 2750 BP.
Cretaceous
"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. 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. The Cretaceous was also an important interval in the evolution of bioerosion, the production of borings and scrapings in rocks, hardgrounds and shells.
Timeline of Cretaceous–Paleogene extinction event research
Ideas that evolution might proceed along pre-ordained patterns or that evolutionary lineages might age, deteriorate, and die like individual animals became popular starting in the late , but were superseded by the Neo-Darwinian synthesis. The aftermath of this transition brought renewed interest to the extinction at the end of the Cretaceous. Paleontologists began dabbling in the subject, proposing environmental changes during the Cretaceous like mountain-building, dropping temperatures or volcanic eruptions as explanation for the extinction of the dinosaurs. Nevertheless, much of the research occurring during this period lacked rigor, evidential support or depended on tenuous assumptions. Michael J. Benton called the years between 1920 and 1970 the "Dilettante Phase" of Cretaceous–Paleogene extinction research.
Paradeshayesites
The International Commission on Stratigraphy (ICS) has assigned the First Appearance Datum of "Paradeshayesites oglanlensis" as the defining biological marker for the start of the Aptian Stage of the Cretaceous, ~125.0 million years ago.
Mesozoic
The Cretaceous is the longest period of the Mesozoic, but has only two epochs: Early and Late Cretaceous.
Deccan Traps
The Deccan Traps began forming 66.25 million years ago, at the end of the Cretaceous period. The bulk of the volcanic eruption occurred at the Western Ghats some 66 million years ago. This series of eruptions may have lasted fewer than 30,000 years.
History of Brittany
The history of Brittany begins with settlement beginning in prehistoric times, beginning around 700 000 BCE. The neolithic era, which began around 5000 BCE, is characterised in the region by the development of an important megalithic art found in sites such as the cairn of Barnenez, the cairn of Gavrinis, the table of the Merchants of Locmariaquer or the alignments of Carnac. In the course of its protohistory which began around the middle of the third century BCE, a subsoil rich in tin allowed the development of an industry in bronze objects, which led to commercial routes for export to other regions of Europe. It was inhabited by Gallic peoples including the Veneti and the Namnetes in the first centuries BCE before these territories were conquered by Julius Caesar in 57 BCE, and progressively Romanized.
Phanerozoic
The Late Cretaceous Epoch spans from 100 million to 66 million years ago. The Late Cretaceous featured a cooling trend that would continue into the Cenozoic Era. Eventually, tropical ecology was restricted to the equator and areas beyond the tropic lines featured extreme seasonal changes of weather. Dinosaurs still thrived as new species such as "Tyrannosaurus", "Ankylosaurus", "Triceratops" and Hadrosaurs dominated the food web. Whether or not Pterosaurs went into a decline as birds radiated is debated, however many families survived until the end of the Cretaceous, alongside new species such as the gigantic "Quetzalcoatlus". Marsupials evolved within the large conifer forests as scavengers. In the oceans, Mosasaurs ruled the seas to fill the role of the ichthyosaurs, and huge plesiosaurs, such as "Elasmosaurus", evolved. Also, the first flowering plants evolved. At the end of the Cretaceous, the Deccan Traps and other volcanic eruptions were poisoning the atmosphere. As this was continued, it is thought that a large meteor smashed into Earth, creating the Chicxulub Crater creating the event known as the K-T Extinction, the fifth and most recent mass extinction event, during which 75% of life on Earth became extinct, including all non-avian dinosaurs. Every living thing with a body mass over 10 kilograms became extinct, and the age of the dinosaurs came to an end.
Paleontology in Oregon
Oregon's islands collided with the Laramidian continent at the end of the Jurassic, creating a new western coastline during the Cretaceous period. This coastline later developed through a combination of sea level change and mountain uplift. Global temperatures reached their maximum during the mid-Cretaceous, melting mountain ice and increasing global sea levels. As sea levels rose the Pacific grew to cover more of Oregon's landmass, eventually stopping at the base of a coastal mountain range. These mountains blocked oceanic weather systems, creating a tropical rainy environment along the ancient Oregonian coast. Although the mountain range ran along that Cretaceous coast, it was different from Oregon's modern Coast Range.
South Asian Stone Age
The South Asian Stone Age covers the Palaeolithic, Mesolithic and Neolithic periods in South Asia. Evidence for the most ancient anatomically modern "Homo sapiens" in South Asia has been found in the cave sites of Cudappah of India, Batadombalena and Belilena in Sri Lanka. In Mehrgarh, in what is today western Pakistan, the Neolithic began c. 7000 BCE and lasted until 3300 BCE and the first beginnings of the Bronze Age. In South India, the Mesolithic lasted until 3000 BCE, and the Neolithic until 1400 BCE, followed by a Megalithic transitional period mostly skipping the Bronze Age. The Iron Age began roughly simultaneously in North and South India, around c. 1200 to 1000 BCE (Painted Grey Ware culture, Hallur).
Phanerozoic
The Early Cretaceous Epoch spans from 145 million to 100 million years ago. The Early Cretaceous saw the expansion of seaways, and as a result, the decline and extinction of sauropods (except in South America). Many coastal shallows were created, and that caused ichthyosaurs to die out. Mosasaurs evolved to replace them as apex species of the seas. Some island-hopping dinosaurs, like "Eustreptospondylus", evolved to cope with the coastal shallows and small islands of ancient Europe. Other dinosaurs, such as "Carcharodontosaurus" and "Spinosaurus", rose to fill the empty space that the Jurassic-Cretaceous extinction had created. Of the most successful would be the "Iguanodon" which spread to every continent. Seasons came back into effect and the poles grew seasonally colder. Dinosaurs such as the "Leaellynasaura" inhabited the polar forests year-round, while many dinosaurs, such as the "Muttaburrasaurus", migrated there during summer . Since it was too cold for crocodiles, it was the last stronghold for large amphibians, such as the "Koolasuchus". In this epoch Pterosaurs reached their maximum diversity and grew larger, as species like "Tapejara" and "Ornithocheirus" took to the skies. The first true birds evolved, possibly sparking competition between them and the pterosaurs.
North American land mammal age
The North American land mammal ages (NALMA) establishes a geologic timescale for North American fauna beginning during the Late Cretaceous and continuing through to the present. These periods are referred to as ages or intervals (or stages when referring to the rock strata of that age) and were established using geographic place names where fossil materials were obtained.
Grotta-Pelos culture
The Grotta-Pelos culture () refers to a "cultural" dating system used for part of the early Bronze Age in Greece. Specifically, it is the period that marks the beginning of the so-called Cycladic culture and spans the Neolithic period in the late 4th millennium BC (ca. 3300 BC), continuing in the Bronze Age to about 2700 BC.
The term was coined by Colin Renfrew, who named it after the sites of Grotta and Pelos on the Cycladic islands of Naxos and Milos, respectively. Other archaeologists prefer a "chronological" dating system and refer to this period as the Early Cycladic I (ECI).
10th millennium BC
The 10th millennium BC spanned the years 10000 through 9001 BC. It marks the beginning of the Mesolithic and Epipaleolithic periods, which is the first part of the Holocene epoch. Agriculture, based on the cultivation of primitive forms of millet and rice, occurred in Southwest Asia. Although agriculture was being developed in the Fertile Crescent, it would not be widely practiced for another 2,000 years.
Climate across Cretaceous–Paleogene boundary
The Cretaceous Period (145–66 Ma), overall, had a relatively warm climate which resulted in high eustatic sea levels and created numerous shallow inland seas. In the Late Cretaceous, the climate was much warmer than present; however, throughout most of the period, a cooling trend is apparent. The tropics were much warmer in the early Cretaceous and became much cooler toward the end of the Cretaceous.
Cretaceous
As with other older geologic periods, the rock beds of the Cretaceous are well identified but the exact age of the system's base is uncertain by a few million years. No great extinction or burst of diversity separates the Cretaceous from the Jurassic. However, the top of the system is sharply defined, being placed at an iridium-rich layer found worldwide that is believed to be associated with the Chicxulub impact crater, with its boundaries circumscribing parts of the Yucatán Peninsula and into the Gulf of Mexico. This layer has been dated at 66.043 Ma.
Antarctic flora
South America, Madagascar, Africa, India, Australia, New Zealand, and Antarctica were all part of the supercontinent Gondwana, which started to break up in the early Cretaceous period (14566 million years ago). India was the first to break away, followed by Africa, and then New Zealand, which started to drift north. By the end of the Cretaceous, South America and Australia were still joined to Antarctica. Paleontologist Gilbert Brenner identified the emergence of a distinct southern Gondwanan flora by the late Cretaceous period in the cooler and humid southern hemisphere regions of Australia, southern South America, southern Africa, Antarctica, and New Zealand; it most resembled the flora of modern-day southern New Zealand. A drier northern Gondwanan flora had developed in northern South America and northern Africa.
List of Indian and Madagascan dinosaurs
The Indian fossil record of dinosaurs is good, with fossils coming from the entire Mesozoic era – starting with the Triassic period (a geological period that started 251.9 million years ago and continued till 201.3 million years ago), to the Jurassic period (201 million years ago to 145 million years ago) and Cretaceous period (from 145 million years ago to 66 million years ago), when globally all non-avian dinosaurs and 65 per cent of all life became extinct. Madagascar also preserves various unique dinosaurs from the Jurassic and Cretaceous.This is a timeline of selected dinosaurs from the list above. Time is measured in Ma, megaannum, along the x-axis.
Cretaceous
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.
Though Gondwana was still intact in the beginning of the Cretaceous, it broke up as South America, Antarctica and Australia rifted away from Africa (though India and Madagascar remained attached to each other); 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. Broad shallow seas advanced across central North America (the Western Interior Seaway) and Europe, then receded late in the period, leaving thick marine deposits sandwiched between coal beds. At the peak of the Cretaceous transgression, one-third of Earth's present land area was submerged.
Prehistory of the United States
During the Late Cretaceous the Gulf of Mexico had expanded through North America until reaching Alaska. Up to half of the continent's modern surface area may have been submerged by this sea. This is called the Western Interior Seaway. It covered the majority of states like Texas, New Mexico, Oklahoma, Colorado, Kansas, Nebraska, the Dakotas, and Wyoming. The seafloor was smooth and probably never submerged by more than 600 feet of water. A great diversity of invertebrates flourished both on the bottom and in the water column. Examples include ammonites, giant clams, crinoids, rudists, and squid. Vertebrate life included bony fishes, mosasaurs, plesiosaurs, sharks, and turtles. Areas now occupied by the plains of the east coast from New Jersey southward as well as the Gulf coast region were covered in seawater during the Cretaceous. Sea levels reached their highest level in all of geologic history during the Cretaceous, although they declined before the period ended. Scleractinian corals were more diverse during the Cretaceous than they are today. Back then coral reefs formed along the Gulf coast. Rudist bivalves also constructed reefs in the Gulf coast region. Another bivalve, Exogyra, was so common its fossils are found in almost every Cretaceous marine deposit. During the Cretaceous, the dominant group of living fishes, the teleosts, first achieved ascendency over their holostean forebears. The aquatic toothed bird Hesperornis is the only known Cretaceous bird whose remains are found with any frequency in North America.
International Commission on Stratigraphy
One such controversy arose in 2009 when the ICS deliberated and decided that the Pliocene Series of the current but unofficially named Quaternary Period should be shifted into the Neogene System and Neogene Period. The term Quaternary has yet to be officially adopted by the IUGS, but has widespread support as acceptable nomenclature for the current geologic period beginning at the GSSP accepted at 5,332,000 years ago at the transition between the Messinian Age to the Zanclean Age (3.6 mya). The ICS voted, perhaps because the time units span human paleo-archaeological strata, to begin the Quaternary at the end GSSP of the Piacenzian Age (2.588 mya) or possibly the end of the Gelasian (1.806 mya), any of which are in a different epoch.
Minoan civilization
The Early Bronze Age (3500 to 2100 BC) has been described as indicating a "promise of greatness" in light of later developments on the island. The Bronze Age began on Crete around 3200 BC. In the late third millennium BC, several locations on the island developed into centers of commerce and handiwork, enabling the upper classes to exercise leadership and expand their influence. It is likely that the original hierarchies of the local elites were replaced by monarchies, a precondition for the palaces.
Paleogene
The Paleogene (; also spelled Palaeogene or Palæogene; informally Lower Tertiary or Early Tertiary) is a geologic period and system that spans 43 million years from the end of the Cretaceous Period million years ago (Mya) to the beginning of the Neogene Period Mya. It is the beginning of the Cenozoic Era of the present Phanerozoic Eon. The Paleogene is most notable for being the time during which mammals diversified from relatively small, simple forms into a large group of diverse animals in the wake of the Cretaceous–Paleogene extinction event that ended the preceding Cretaceous Period. The United States Geological Survey uses the abbreviation P for the Paleogene.
Cracidae
In addition, the molecular data suggest that the Cracidae originated in the Late Cretaceous, but the authors caution that this cannot be more than a hypothesis at present: as the rate of molecular evolution is neither constant over time nor uniform between genera and even species, dating based on molecular information has a very low accuracy over such long timespans and needs to be corroborated by fossil evidence. The fossil record of cracids is limited to a single doubtfully distinct genus of chachalaca, "Boreortalis" (Hawthorn Early Miocene of Florida, USA; may actually be a junior synonym of "Ortalis") and some species in the modern genus "Ortalis", however. This does not provide any assistance in evaluating the hypothesis (Pereira "et al.", 2002) that the split between the 4 main lineages of our time occurred quite rapidly, approximately in the Oligocene or slightly earlier, somewhere between 40 and 20 mya.
Prehistory and protohistory of Poland
Poland's Bronze Age comprised Period I, c. 2300–1600 BC; Period II, c. 1600–1350 BC; Period III, c. 1350–1100 BC; Period IV, c. 1100–900 BC; and Period V, c. 900–700 BC. The Early Iron Age included Hallstatt Period C, c. 700–600 BC, and Hallstatt Period D, c. 600–450 BC.
Poland's Bronze- and Iron-Age cultures are known mainly from archeological research. Poland's Early Bronze Age cultures began around 2300-2400 BC, whereas the Iron Age commenced c. 700-750 BC. By the beginning of the Common Era, the Iron Age archeological cultures described in the main article no longer existed. Given the absence of written records, the ethnicities and linguistic affiliations of the groups living in Central and Eastern Europe at that time are speculative; there is considerable disagreement about their identities. In Poland, the Lusatian culture, which spanned the Bronze and Iron Ages, became particularly prominent. The most famous archeological discovery from that period is the Biskupin fortified settlement ("gród") that represented early-Iron-Age Lusatian culture.
Cretaceous
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 which lies between the Mesozoic and Cenozoic eras.
Mesozoic
The Late Cretaceous spans from 100 to 66 million years ago. The Late Cretaceous featured a cooling trend that would continue in the Cenozoic era. Eventually, tropics were restricted to the equator and areas beyond the tropic lines experienced extreme seasonal changes in weather. Dinosaurs still thrived, as new taxa such as "Tyrannosaurus", "Ankylosaurus", "Triceratops" and hadrosaurs dominated the food web. In the oceans, mosasaurs ruled, filling the role of the ichthyosaurs, which, after declining, had disappeared in the Cenomanian-Turonian boundary event. Though pliosaurs had gone extinct in the same event, long-necked plesiosaurs such as "Elasmosaurus" continued to thrive. Flowering plants, possibly appearing as far back as the Triassic, became truly dominant for the first time. Pterosaurs in the Late Cretaceous declined for poorly understood reasons, though this might be due to tendencies of the fossil record, as their diversity seems to be much higher than previously thought. Birds became increasingly common and diversified into a variety of enantiornithe and ornithurine forms. Though mostly small, marine hesperornithes became relatively large and flightless, adapted to life in the open sea. Metatherians and primitive eutherian also became common and even produced large and specialised genera like "Didelphodon" and "Schowalteria". Still, the dominant mammals were multituberculates, cimolodonts in the north and gondwanatheres in the south. At the end of the Cretaceous, the Deccan traps and other volcanic eruptions were poisoning the atmosphere. As this continued, it is thought that a large meteor smashed into earth 66 million years ago, creating the Chicxulub Crater in an event known as the K-Pg Extinction (formerly K-T), the fifth and most recent mass extinction event, in which 75% of life became extinct, including all non-avian dinosaurs. Everything over 10 kilograms became extinct. The age of the dinosaurs was over.
Cradle of civilization
Around 10,200 BC the first fully developed Neolithic cultures belonging to the phases Pre-Pottery Neolithic A (PPNA) and Pre-Pottery Neolithic B (7600 to 6000 BC) appeared in the Fertile Crescent and from there spread eastwards and westwards. One of the most notable PPNA settlements is Jericho in the Levant region, thought to be the world's first town (settled around 8500 BC and fortified around 6800 BC). In Mesopotamia, the convergence of the Tigris and Euphrates rivers produced rich fertile soil and a supply of water for irrigation. The civilizations that emerged around these rivers are among the earliest known non-nomadic agrarian societies. It is because of this that the Fertile Crescent region, and Mesopotamia in particular, are often referred to as the cradle of civilization. The period known as the Ubaid period (c. 6500 to 3800 BC) is the earliest known period on the alluvial plain, although it is likely earlier periods exist obscured under the alluvium. It was during the Ubaid period that the movement towards urbanization began. Agriculture and animal husbandry were widely practiced in sedentary communities, particularly in Northern Mesopotamia, and intensive irrigated hydraulic agriculture began to be practiced in the south.
Tertiary
Tertiary is the former term for the geologic period from 66 million to 2.58 million years ago, a timespan that occurs between the superseded Secondary period and the Quaternary. The Tertiary is no longer recognized as a formal unit by the International Commission on Stratigraphy, but the word is still widely used. The traditional span of the Tertiary has been divided between the Paleogene and Neogene periods and extends to the first stage of the Pleistocene Epoch, the Gelasian stage. 
The period began with the demise of the non-avian dinosaurs in the Cretaceous–Paleogene extinction event, at the start of the Cenozoic Era, and extended to the beginning of the Quaternary glaciation at the end of the Pliocene Epoch.
Dacian art
Dacian civilization went through several stages of development, from the Thracian stage in the Bronze Age to the classical period of the Geto-Dacians (the first century BC to the first century AD). In the Bronze Age, proto-Thracian populations emerged from the fusion of the local Eneolithic (Chalcolithic) stock with the intruders of the transitional Indo-Europeanization Period. From these proto-Thracians, in the Iron Age, there were developed the Dacians of the Danubian-Carpathian Area on the one hand and the Thracians of the eastern Balkan Peninsula on the other.
Timeline of glaciation
There have been five or six major ice ages in the history of Earth over the past 3 billion years. 
The Late Cenozoic Ice Age began 34 million years ago, its latest phase being the Quaternary glaciation, in progress since 2.58 million years ago.
Cretaceous
The cooling trend of the last epoch of the Jurassic continued into the first age of the Cretaceous. There is evidence that snowfalls were common in the higher latitudes and the tropics became wetter than during the Triassic and Jurassic. Glaciation was however restricted to high-latitude mountains, though seasonal snow may have existed farther from the poles. 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.
History of Earth
The Hadean eon represents the time before a reliable (fossil) record of life; it began with the formation of the planet and ended 4.0 billion years ago. The following Archean and Proterozoic eons produced the beginnings of life on Earth and its earliest evolution. The succeeding eon is the Phanerozoic, divided into three eras: the Palaeozoic, an era of arthropods, fishes, and the first life on land; the Mesozoic, which spanned the rise, reign, and climactic extinction of the non-avian dinosaurs; and the Cenozoic, which saw the rise of mammals. Recognizable humans emerged at most 2 million years ago, a vanishingly small period on the geological scale.
Holocene
The Holocene () is the current geological epoch. It began approximately 11,650 cal years before present, after the last glacial period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene together form the Quaternary period. The Holocene has been identified with the current warm period, known as MIS 1. It is considered by some to be an interglacial period within the Pleistocene Epoch.
Cretaceous
Flowering plants (angiosperms) spread during this period, although they did not become predominant until the Campanian Age near the end of the period. Their evolution was aided by the appearance of bees; in fact angiosperms and insects are a good example of coevolution. The first representatives of many leafy trees, including figs, planes and magnolias, appeared in the Cretaceous.
Tarfaya Basin
As sea levels began to rise again during the early Cretaceous, the exposed Jurassic shelf was flooded. Increased temperatures during the Cretaceous, along with increased erosion inland, resulted in the transport of large amounts of clastic materials. Fine-grained clastics formed the basis of deltaic complexes along the coastal margin. Increased accommodation space during highstands allowed for the deposition of silty material over the carbonates of the former Jurassic shelf. These silty materials eventually buried the carbonates as prograding deltas developed in the Early Cretaceous. Within these deltaic sequeneces, a number of shale units were deposited.
Isle of Wight
The Isle of Wight is made up of a variety of rock types dating from early Cretaceous (around 127 million years ago) to the middle of the Palaeogene (around 30 million years ago). The geological structure is dominated by a large monocline which causes a marked change in age of strata from the northern younger Tertiary beds to the older Cretaceous beds of the south. This gives rise to a dip of almost 90 degrees in the chalk beds, seen best at the Needles.
Prehistory of the United States
The beginning of the Cenozoic was also the beginning of the Age of Mammals. The small shrew-like generalist insectivores that survived the Late Cretaceous extinction event began diversifying into the mammals that dominate the modern world's terrestrial ecosystems. The creodonts, which first appeared in the Paleocene, were among the first mammals to specialize in carnivory. The coastal region of the southeastern states, like Alabama and Mississippi were covered in seawater and home to the primitive whale "Basilosaurus" during the Eocene. The diversity of mammalian carnivores on land increased from the Eocene to the Miocene.
Evolution of insects
There are a large number of important fossil sites worldwide containing beetles from the Cretaceous. Most of them are located in Europe and Asia and belong to the temperate climate zone during the Cretaceous. A few of the fossil sites mentioned in the chapter Jurassic also shed some light on the early cretaceous beetle fauna (e.g. the Yixian formation in Liaoning, North China). Further important sites from the Lower Cretaceous include the Crato Fossil Beds in the Araripe basin in the Ceará, North Brazil as well as overlying Santana formation, with the latter was situated near the paleoequator, or the position of the earth's equator in the geologic past as defined for a specific geologic period. In Spain there are important sites near Montsec and Las Hoyas. In Australia the Koonwarra fossil beds of the Korumburra group, South Gippsland, Victoria is noteworthy. Important fossil sites from the Upper Cretaceous are Kzyl-Dzhar in South Kazakhstan and Arkagala in Russia.
Cretaceous Dawn
Cretaceous Dawn is a science-fiction novel by sibling scientists Lisa M. Graziano and Michael S. A. Graziano, published in 2008 by Leapfrog Press (initially published as 'Hell Creek: 65 Million Years in the Past, the Journey Begins' under Trafford Publishing in 2006. The book contains 304 pages. Its story is set to a modern time and also to the prehistory of 65 million years ago (at the end of the Cretaceous era). It starts in the physics laboratory, where long-extinct beetles start to appear. Four people and a dog are then hurled 65 million years through the deep geologic time, to the ending era of the dinosaurs (Hell Creek formation), and the main character - paleontologist Julian Whitney and his companions - have only one chance for their own rescue.
Japan Trench
During the Cretaceous (145.5-66 million years ago) to early Paleogene (66-23.03 ma), evidence of andesitic volcanism along with the development of a large syncline and a thickened sediment sequence indicate the possible development of a forearc basin. Activity during the Cretaceous included subduction events as well as extensive accretion of sediment to the Northeastern Japan Arc that continues today. Volcanism decreased during the early Paleogene (66 ma), exposing the thickened Cretaceous-Paleogene 160-km thick sediment sequence. Once this sediment sequence subsided, volcanism once again resumed.
Prehistory of the United States
After the Cretaceous, a new era of geologic time began; the Cenozoic era, which means the era of "recent life". Traditionally, the first period of the Cenozoic was called the Tertiary, however recent recommendations of the International Commission on Stratigraphy discourage its use, with the correspondent time span divided between the earlier Paleogene and the more recent Neogene periods. The geologic turmoil on the west coast was maintained as the Pacific Plate continued to slide under the North American Plate. During the early part of the Cenozoic period climates were much warmer than they are today. Latitudes as high as South Dakota had a subtropical climate until as recently as the end of the Oligocene.
Late Cenozoic Ice Age
The Earth is currently in an interglacial period which began 11,700 years ago. It is traditionally referred to as the Holocene Epoch, separate from the Pleistocene Epoch. However, there is no evidence that its actually separate. At this time, it appears to be an interglacial period within the Pleistocene Epoch. This period can also be referred to as the Holocene Interglacial or Holocene Interstadial.
Jurassic
The Jurassic (; from Jura Mountains) was a geologic period and system that spanned 56 million years from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period Mya. The Jurassic constitutes the middle period of the Mesozoic Era, also known as the Age of Reptiles. The start of the period was marked by the major Triassic–Jurassic extinction event. Two other extinction events occurred during the period: the Pliensbachian-Toarcian extinction in the Early Jurassic, and the Tithonian event at the end; however, neither event ranks among the "Big Five" mass extinctions.
Evolutionary history of life
Ediacara biota appear during the Ediacaran period, while vertebrates, along with most other modern phyla originated about during the Cambrian explosion. During the Permian period, synapsids, including the ancestors of mammals, dominated the land, but most of this group became extinct in the Permian–Triassic extinction event . During the recovery from this catastrophe, archosaurs became the most abundant land vertebrates; one archosaur group, the dinosaurs, dominated the Jurassic and Cretaceous periods. After the Cretaceous–Paleogene extinction event killed off the non-avian dinosaurs, mammals increased rapidly in size and diversity. Such mass extinctions may have accelerated evolution by providing opportunities for new groups of organisms to diversify.
Mesozoic
The Early Cretaceous spans from 145 to 100 million years ago. The Early Cretaceous saw the expansion of seaways, and as a result, the decline and extinction of sauropods (except in South America). Some island-hopping dinosaurs, like "Eustreptospondylus", evolved to cope with the coastal shallows and small islands of ancient Europe. Other dinosaurs rose up to fill the empty space that the Jurassic-Cretaceous extinction left behind, such as "Carcharodontosaurus" and "Spinosaurus". Of the most successful was the "Iguanodon", which spread to every continent. Seasons came back into effect and the poles got seasonally colder, but some dinosaurs still inhabited the polar forests year round, such as "Leaellynasaura" and "Muttaburrasaurus". The poles were too cold for crocodiles, and became the last stronghold for large amphibians like "Koolasuchus". Pterosaurs got larger as genera like "Tapejara" and "Ornithocheirus" evolved. Mammals continued to expand their range: eutriconodonts produced fairly large, wolverine-like predators like "Repenomamus" and "Gobiconodon", early therians began to expand into metatherians and eutherians, and cimolodont multituberculates went on to become common in the fossil record.
Geology of the southern North Sea
The break up of Pangea occurs during the Kimmerian tectonic phase for most of the Mesozoic, until the early-mid Cretaceous, this marks the start of creating the present position of our continents today. During the Jurassic, rifting activity reaches its maximum and North America starts to move apart from Eurasia following that event in the Cretaceous the southern part of North America starts to open up the Atlantic Ocean with the separation of South America and Africa. At the end of the Mesozoic the North Sea reached its final position where it lies in present day. Throughout the Cretaceous rifting eventually slowed down and came to a halt which later created the North Sea failed rift system because the regional stresses had shifted on to North America. The Jurassic is probably the most important geological time for hydrocarbon exploration in the North Sea. Many accumulations are in Jurassic reservoir, the Kimmeridge clay is considered the most important source rock and structures formed during rifting form excellent traps. In the first place rifting was responsible for the deposition of organic rich source rock due to anoxic conditions in the deep isolated rift basins. Possibly the most important phase to create structures and traps for the natural resources we try to collect today.
Crete
The first human settlement in Crete dates before 130,000 years ago, during the Paleolithic age. Settlements dating to the aceramic Neolithic in the 7th millennium BC, used cattle, sheep, goats, pigs and dogs as well as domesticated cereals and legumes; ancient Knossos was the site of one of these major Neolithic (then later Minoan) sites. Other neolithic settlements include those at Kephala, Magasa, and Trapeza.
Polar forests of the Cretaceous
During the Cretaceous, temperate forests thrived at polar latitudes, as there was a notable difference from current conditions at high latitudes during the Cretaceous polar seasons. The duration of summer sunlight and winter darkness lasted for approximately 5 months each. This variation in light is thought to have played a critical role in the composition and evolution of polar forests. Fossilized flora evidence suggests the presence of paleoforests up to latitudes of 85° in both Northern and Southern hemispheres. The dominant forms of vegetation at these high latitudes during the previous 100 million years were rapidly evolving and ultimately being replaced during a time known as the Cretaceous Terrestrial Revolution. During the Cretaceous Terrestrial Revolution, conifers, cycads and ferns were selectively replaced by angiosperms and gymnosperms, becoming the main species dominating the high paleolatitudes. In this Cretaceous greenhouse world, Arctic conifer forests were considered predominantly deciduous, while those that grew on Antarctica contained a significantly greater proportion of evergreens.
Timeline of Cretaceous–Paleogene extinction event research
Paleontologists have recognized that a significant transition occurred between the Mesozoic and Cenozoic eras at least since the . Around this time dinosaur fossils were first being described in the scientific literature. Nevertheless, so few dinosaurs were known that the significance of their passing went unrecognized and little scientific effort was exerted toward finding an explanation. As more and more different kinds of dinosaurs were discovered, their extinction and replacement by mammals was recognized as significant but dismissed with little examination as a natural consequence of the mammals' supposed innate superiority. Consequently, paleontologist Michael J. Benton has called the years up to 1920 as the "Nonquestion Phase" of Cretaceous–Paleogene extinction research.
Antarctica
Africa separated from Antarctica in the Jurassic, around 160 Ma, followed by the Indian subcontinent in the early Cretaceous (about 125 Ma). By the end of the Cretaceous, about 66 Ma, Antarctica (then connected to Australia) still had a subtropical climate and flora, complete with a marsupial fauna. In the Eocene epoch, about 40 Ma Australia-New Guinea separated from Antarctica, so that latitudinal currents could isolate Antarctica from Australia, and the first ice began to appear. During the Eocene–Oligocene extinction event about 34 million years ago, CO levels have been found to be about 760 ppm and had been decreasing from earlier levels in the thousands of ppm.
Mesoamerican Archaic period
The Archaic period, also known as the preceramic period, is a period in Mesoamerican chronology that begins around 8000 BCE and ends around 2000 BCE and is generally divided into Early, Middle, and Late Archaic periods. The period is preceded by the Paleoindian (or Lithic) period and followed by the Preclassic period. Scholars have found it difficult to determine exactly when the Paleoindian period ends and the Archaic begins, but it is generally linked with changing climate associated with the transition from the Pleistocene to the Holocene epochs, and absence of extinct Pleistocene animals. It is also generally unclear when the Archaic period ends and the Preclassic period begins, though the appearance of pottery, large-scale agriculture, and villages signal the transition.
South Polar region of the Cretaceous
In the Early Cretaceous, East Gondwana (Australia, Antarctica and Zealandia) had started to split away from South America, and India and Madagascar also began to separate at around the same time. The tropical zone may have extended, during the Cretaceous, to 32°S, allowing year-round tree growth in the Antarctic in polar forests. The discovery of several mature evergreen and deciduous trees indicate a warm-to-cool temperature with moderate seasons lacking widespread freezing, at least between the latitudes 70 and 85°S. However, it is also possible that the plant life may only be representative of the warm summer months. Much of what is known of the plant life of East Gondwana during the Cretaceous consists of pollen remains and leaf compressions from the northern Antarctic Peninsula. Depending on the latitude, the polar winters may have lasted from six weeks to four and a half months.
However, rocks from the Early Cretaceous Wonthaggi Formation in southeastern Australia evidence seasonally frozen ground. Its geographical positioning in the Early Cretaceous at around 78°S indicates this area experienced one to three months of darkness in winters, and this area is representative of a glacial-fed floodplain. Evidence of Early Cretaceous glaciation and cold climates was discovered in sediments in the Eromanga Basin in modern-day central Australia, or 60 to 80°S in the Early Cretaceous. This basin was a large inland sea in the Cretaceous. Nonetheless, similar formations could have been created by simply debris flow, and so it is possible that glaciation did not ever occur there. The total polar ice coverage during the Mesozoic may have been a third of the size as it is in modern times, though cold snaps of subfreezing temperatures possibly occurred throughout the Early Cretaceous.
Climate across Cretaceous–Paleogene boundary
The K–Pg (formerly K–T) boundary is a thin band of sediment that dates back to 66 million years ago, and is found as a consistent layer all over the planet in over 100 known different locations. K and T are the abbreviations for the Cretaceous and Tertiary periods, respectively, but the name Tertiary has been replaced by "Paleogene" as a formal time or rock unit by the International Commission on Stratigraphy, and Pg is now the abbreviation. This boundary marks the start of the Cenozoic Era. Non-avian dinosaur fossils are found only below the K–Pg boundary which indicates that they became extinct at this event. In addition, mosasaurs, plesiosaurs, pterosaurs and many species of plants and invertebrates do not occur above this boundary, indicating extinction. The boundary was found to be enriched in iridium many times greater than normal (30 times background in Italy and 160 times at Stevns, Denmark), most likely indicating an extraterrestrial event or volcanic activity associated with this interval. Rates of extinction and radiation varied across different clades of organisms.
Meghalayan
The Meghalayan begins 4,200 years BP, i.e., before 1950 ( 2250 BCE), leaving open room for the possible creation of the Anthropocene from 1950 forward. The age began with a 200-year drought that impacted human civilizations in Egypt, Greece, Syria, Canaan, Mesopotamia, the Indus Valley and the Yangtze River Valley. "The fact that the beginning of this age coincides with a cultural shift caused by a global climate event makes it unique," according to Stanley Finney, Secretary General of the International Union of Geological Sciences.
Mesangiospermae
Molecular clock comparisons of DNA sequences indicate that the mesangiosperms originated between 140 and 150 Mya (million years ago) near the beginning of the Cretaceous period. This was about 25 Ma (million years) after the origin of the angiosperms in the mid-Jurassic.
Geology of Chile
The formation of the Andes began during the Jurassic. During the Cretaceous, the Andes began to assume their present form by the uplifting, faulting and folding of sedimentary and metamorphic rocks of ancient cratons. Tectonic forces along the subduction zone along the west coast of South America continue to their orogenesis, resulting in earthquakes and volcanic eruptions to this day.
Early Cretaceous
The Early Cretaceous (geochronological name) or the Lower Cretaceous (chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 146 Ma to 100 Ma.
Prehistory of the United States
The Cenozoic era began afterward. The inland sea of the Cretaceous gradually vanished and mammals were beginning to dominate the land. During the Eocene the western states were home to small primitive camels and horses as well as the carnivorous creodonts. Soon mammals had entered the oceans and the early whale "Basilosaurus" swam the coastal waters of the southeast. Rhino-like titanotheres dominated Oligocene South Dakota. From this point on the climate in the United States cooled until the Pleistocene, when glaciers spread. Saber-toothed cats, woolly mammoths, mastodons, and dire wolves roamed the land. Humans arrived across a land bridge between Siberia and Alaska and may have played a role in hunting these animals into extinction.
Eudromaeosauria
Eudromaeosaur fossils are known almost exclusively from the northern hemisphere. They first appeared in the early Cretaceous Period (early Aptian stage, about 124 million years ago) and survived until the end of the Cretaceous (Maastrichtian stage, Ma). The earliest known definitive eudromaeosaur is the dromaeosaurine "Utahraptor ostrommaysorum", from the Cedar Mountain Formation, dated to 124 million years ago. However, the earlier (143-million-year-old) fossils such as those of "Nuthetes destructor" and several indeterminate teeth dating to the Kimmeridgian stage may represent eudromaeosaurs.
Eocene
The Eocene () Epoch, lasting from , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Paleocene Epoch to the beginning of the Oligocene Epoch. The start of the Eocene is marked by a brief period in which the concentration of the carbon isotope C in the atmosphere was exceptionally low in comparison with the more common isotope C. The end is set at a major extinction event called the "Grande Coupure" (the "Great Break" in continuity) or the Eocene–Oligocene extinction event, which may be related to the impact of one or more large bolides in Siberia and in what is now Chesapeake Bay. As with other geologic periods, the strata that define the start and end of the epoch are well identified, though their exact dates are slightly uncertain.
Geology of the Bryce Canyon area
The exposed geology of the Bryce Canyon area in Utah shows a record of deposition that covers the last part of the Cretaceous Period and the first half of the Cenozoic era in that part of North America. The ancient depositional environment of the region around what is now Bryce Canyon National Park varied from the warm shallow sea (called the Cretaceous Seaway) in which the Dakota Sandstone and the Tropic Shale were deposited to the cool streams and lakes that contributed sediment to the colorful Claron Formation that dominates the park's amphitheaters.
Cretolamna
These sharks lived from the Aptian of the Cretaceous period to the Ypresian stage of the early Eocene epoch (115 to 48 million years ago). It is considered by many to be the ancestor of many of the famous shark genera, such as the mako, great white, "Carcharocles angustidens", and "Carcharocles megalodon" sharks.
Timeline of Cretaceous–Paleogene extinction event research
Since the 19th century, a significant amount of research has been conducted on the Cretaceous–Paleogene extinction event, the mass extinction that ended the dinosaur-dominated Mesozoic Era and set the stage for the Age of Mammals, or Cenozoic Era. A chronology of this research is presented here.
Fossil record of fire
Fires again become significant in the late Jurassic through the Cretaceous. They are especially useful as charcoalified flowers provide a key piece of evidence for tracking the origin of the angiosperm lineage. Contrary to popular perception, there is no evidence of a global inferno at the end of the Cretaceous, when the dinosaurs became extinct; the record of fire after this point is somewhat sparse until the advent of human intervention around half a million years ago, although this may be biased by a lack of investigations from this period.
History of Croatia before the Croats
As the Stone Age moved into the Bronze Age, known as the Eneolithic period, in which the first metal – copper – began to be used, the Vučedol culture arose (c. 3000 BC – c. 2200 BC), named after the locality of Vučedol, on the bank of the Danube near Vukovar. Vučedol, near Vukovar, an important prehistoric site (‘The Troy of the Danube’), after which the Vučedol culture was named, and which embraced a wider cultural complex from the Carpathians to the eastern Alps and the Dinaric Alps. It is presumed to have emerged after the arrival of Indo-European settlers around 3,000 BC and lasted until about 2,000 BC. Its characteristics include new metalwork procedures, extremely skilled ceramics, and, according to some researchers, the people used a calendar marked on ceramic vessels.
Cretaceous
From youngest to oldest, the subdivisions of the Cretaceous period are:
Evolution of insects
The Cretaceous () had much of the same insect fauna as the Jurassic until much later on. During the Cretaceous, the late-Paleozoic-to-early-Mesozoic supercontinent of Pangaea completed its tectonic breakup into present day continents, although their positions were substantially different at the time. As the Atlantic Ocean widened, the convergent-margin 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. Though Gondwana was still intact in the beginning of the Cretaceous, it broke up as South America, Antarctica and Australia rifted away from Africa (though India and Madagascar remained attached to each other); 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. Broad shallow seas advanced across central North America (the Western Interior Seaway) and Europe, then receded late in the period, leaving thick marine deposits sandwiched between coal beds.
Ancient history
The Archaic Period in Greece is generally considered to have lasted from around the eighth century BC to the invasion by Xerxes in 480 BC. This period saw the expansion of the Greek world around the Mediterranean, with the founding of Greek city-states as far afield as Sicily in the West and the Black sea in the East. Politically, the Archaic period in Greece saw the collapse of the power of the old aristocracies, with democratic reforms in Athens and the development of Sparta's unique constitution. The end of the Archaic period also saw the rise of Athens, which would come to be a dominant power in the Classical period, after the reforms of Solon and the tyranny of Pisistratus.
Aptian
The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous epoch or series and encompasses the time from 125.0 ± 1.0 Ma to 113.0 ± 1.0 Ma (million years ago), approximately. The Aptian succeeds the Barremian and precedes the Albian, all part of the Lower/Early Cretaceous.
Gondwana
The first phases of Andean orogeny in the Jurassic and Early Cretaceous were characterized by extensional tectonics, rifting, the development of back-arc basins and the emplacement of large batholiths. This development is presumed to have been linked to the subduction of cold oceanic lithosphere. During the mid to Late Cretaceous (ca. 90 million years ago) the Andean orogeny changed significantly in character. Warmer and younger oceanic lithosphere is believed to have started to be subducted beneath South America around this time. Such kind of subduction is held responsible not only for the intense contractional deformation that different lithologies were subject to, but also the uplift and erosion known to have occurred from the Late Cretaceous onward. Plate tectonic reorganization since the mid-Cretaceous might also have been linked to the opening of the South Atlantic Ocean. Another change related to mid-Cretaceous plate tectonic changes was the change of subduction direction of the oceanic lithosphere that went from having south-east motion to having a north-east motion at about 90 million years ago. While subduction direction changed it remained oblique (and not perpendicular) to the coast of South America, and the direction change affected several subduction zone-parallel faults including Atacama, Domeyko and Liquiñe-Ofqui.
Evolution of cetaceans
The aquatic lifestyle of cetaceans first began in the Indian subcontinent from even-toed ungulates 50 million years ago, over a period of at least 15 million years, however a jawbone discovered in Antarctica may reduce this to 5 million years. Archaeoceti is an extinct parvorder of Cetacea containing ancient whales. The traditional theory of cetacean evolution, first proposed by Van Valen in 1966, was that whales were related to the mesonychids, an extinct order of carnivorous ungulates (hoofed animals) that resembled wolves with hooves and were a sister group of the artiodactyls (even-toed ungulates). This theory arose due to similarities between the unusual triangular teeth of the mesonychids and those of early whales. However, molecular phylogeny data indicates that whales are very closely related to the artiodactyls, with hippopotamuses as their closest living relative. Because of this, cetaceans and hippopotamuses are placed in the same suborder, Whippomorpha. Cetartiodactyla (formed from the words Cetacea and Artiodactyla) is a proposed name for an order containing both cetaceans and artiodactyls. However, the earliest anthracotheres, the ancestors of hippos, do not appear in the fossil record until the Middle Eocene, millions of years after "Pakicetus", the first known whale ancestor, appeared during the Early Eocene, implying the two groups diverged well before the Eocene. Since molecular analysis identifies artiodactyls as being very closely related to cetaceans, mesonychids are probably an offshoot from Artiodactyla, and cetaceans did not derive directly from them, but possibly sharing a common ancestor.
Andes
The formation of the modern Andes began with the events of the Triassic when Pangaea began the break up that resulted in developing several rifts. The development continued through the Jurassic Period. It was during the Cretaceous Period that the Andes began to take their present form, by the uplifting, faulting and folding of sedimentary and metamorphic rocks of the ancient cratons to the east. The rise of the Andes has not been constant, as different regions have had different degrees of tectonic stress, uplift, and erosion.
Cretaceous Thermal Maximum
From 250 to 150 Ma, Pangaea covered the Earth's surface, forming one super continent and one gargantuan ocean. During the breakup of Pangaea from 150 to 130 Ma, the Atlantic Ocean began to form the "Atlantic Gateway". Geological records from both the Deep Sea Drilling Project (DSDP) and the Ocean Drilling Program (ODP) support the enhancement of the CTM by the rifting of the Atlantic Ocean. Rising atmospheric carbon dioxide is thought to have been enhanced by the changing geography of the oceans. While rising carbon dioxide levels caused increased global warming, the climate models of the Cretaceous period do not show such elevated global temperatures due to the Earth's carbon dioxide variations. Geologic records show evidence of dissociation of methane clathrates, which causes a rise in carbon dioxide, as the oxygen gas in the atmosphere will readily combine with the dissociated carbon atom from methane.
Late Cretaceous
The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series. The Cretaceous is named after the white limestone known as chalk which occurs widely in northern France and is seen in the white cliffs of south-eastern England, and which dates from this time.
Maastrichtian
The Maastrichtian () is, in the ICS geologic timescale, the latest age (uppermost stage) 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 . The Maastrichtian was preceded by the Campanian and succeeded by the Danian (part of the Paleogene and Paleocene).
Tethys Ocean
Between the Jurassic and the Late Cretaceous, which started about 100 Mya, Gondwana began breaking up, pushing Africa and India north across the Tethys and opening up the Indian Ocean. As these land masses crowded in on the Tethys Ocean from all sides, to as recently as the Late Miocene, 15 Mya, the ocean continued to shrink, becoming the Tethys Seaway or second Tethys Sea. Throughout the Cenozoic (66 million to the dawn of the Neogene, 23 Mya), global sea levels fell hundreds of meters, and eventually the connections between the Atlantic and the Tethys closed off in what is now the Middle East.
Geology of England
The Mesozoic comprises the Triassic, Jurassic and Cretaceous periods (251–66 Ma).
Primate
The primate lineage is thought to go back at least near the Cretaceous–Paleogene boundary or around 63–74 (mya), even though the oldest known primates from the fossil record date to the Late Paleocene of Africa ("Altiatlasius") or the Paleocene-Eocene transition in the northern continents, c. 55 mya ("Cantius", "Donrussellia", "Altanius", "Plesiadapis" and "Teilhardina"). Other studies, including molecular clock studies, have estimated the origin of the primate branch to have been in the mid-Cretaceous period, around 85 mya.
Cretaceous Research
Cretaceous Research is a bimonthly peer-reviewed scientific journal published by Elsevier. The journal focuses on topics dealing with the Cretaceous period and the Cretaceous–Paleogene boundary.
Cretaceous
After the end of the first age, however, temperatures increased again, and these conditions were almost constant until the end of the period. The warming may have been due to intense volcanic activity which produced large quantities of carbon dioxide. Between 70–69 Ma and 66–65 Ma, isotopic ratios indicate elevated atmospheric CO pressures with levels of 1000–1400 ppmV and mean annual temperatures in west Texas between 21 and 23 °C (70-73 °F). Atmospheric CO and temperature relations indicate a doubling of pCO was accompanied by a ~0.6 °C increase in temperature. The production of large quantities of magma, variously attributed to mantle plumes or to extensional tectonics, 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.
History of Croatia before the Croats
In the Bronze Age (c. 2500 BC – c. 800 BC), a period of great ethnic strife and migration, metalwork and techniques for producing bronze items continued to develop. Several cultural groups can be singled out (the Gradina (hillfort) culture in Istria, the Urnfield culture in northern Croatia, the Cetina culture in Dalmatia, etc.), which arose through the symbiosis of earlier cultural traditions and the various influences of strong neighbouring cultures.
Geology of the United States
Once again, during the Cretaceous Period (144-65 million years ago), record high sea levels flooded the continental interior with shallow seas.
Alternatives to evolution by natural selection
Catastrophism has found a place in modern biology with the Cretaceous–Paleogene extinction event at the end of the Cretaceous period, as proposed in a paper by 
Walter and Luis Alvarez in 1980. It argued that a asteroid struck Earth 66 million years ago at the end of the Cretaceous period. The event, whatever it was, made about 70% of all species extinct, including the dinosaurs, leaving behind the Cretaceous–Paleogene boundary. In 1990, a candidate crater marking the impact was identified at Chicxulub in the Yucatán Peninsula of Mexico.
Cretaceous
Late Cretaceous
Late Cretaceous
The Cretaceous–Paleogene extinction event was a large-scale mass extinction of animal and plant species in a geologically short period of time, approximately (Ma). It is widely known as the "K–T extinction event" and is associated with a geological signature, usually a thin band dated to that time and found in various parts of the world, known as the Cretaceous–Paleogene boundary (K–T boundary). "K" is the traditional abbreviation for the Cretaceous Period derived from the German name "Kreidezeit", and "T" is the abbreviation for the Tertiary Period (a historical term for the period of time now covered by the Paleogene and Neogene periods). The event marks the end of the Mesozoic Era and the beginning of the Cenozoic Era. "Tertiary" being no longer recognized as a formal time or rock unit by the International Commission on Stratigraphy, the K-T event is now called the Cretaceous—Paleogene (or K-Pg) extinction event by many researchers.
Pleistocene
In 2009 the International Union of Geological Sciences (IUGS) confirmed a change in time period for the Pleistocene, changing the start date from 1.806 to 2.588 million years BP, and accepted the base of the Gelasian as the base of the Pleistocene, namely the base of the Monte San Nicola GSSP. The IUGS has yet to approve a type section, Global Boundary Stratotype Section and Point (GSSP), for the upper Pleistocene/Holocene boundary ("i.e." the upper boundary). The proposed section is the "North Greenland Ice Core Project" ice core 75° 06' N 42° 18' W. The lower boundary of the Pleistocene Series is formally defined magnetostratigraphically as the base of the Matuyama (C2r) chronozone, isotopic stage 103. Above this point there are notable extinctions of the calcareous nanofossils: "Discoaster pentaradiatus" and "Discoaster surculus".
Gelasian
The Gelasian is an age in the international geologic timescale or a stage in chronostratigraphy, being the earliest or lowest subdivision of the Quaternary period/system and Pleistocene epoch/series. It spans the time between 2.588 ± 0.005 Ma (million years ago) and 1.806 ± 0.005 Ma. It follows the Piacenzian stage (part of the Pliocene) and is followed by the Calabrian stage.
Evolution of tetrapods
The Cenozoic era began with the end of the Mesozoic era and the Cretaceous epoch; and continues to this day. The beginning of the Cenozoic was marked by the Cretaceous-Paleogene extinction event during which all non-avian dinosaurs became extinct. The Cenozoic is sometimes called the "Age of Mammals".
Late Cenozoic Ice Age
The Late Cenozoic Ice Age, Holarctic-Antarctic Ice Age or Antarctic Glaciation began 33.9 million years ago at the Eocene-Oligocene Boundary and is ongoing. It is Earth's current ice age or icehouse period. Its beginning is marked by the formation of the Antarctic ice sheets. The Late Cenozoic Ice Age gets its name due to the fact that it covers roughly the last half of Cenozoic Era so far.