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149-470: Much of the world's modern vertebrate diversity originated in a rapid surge of diversification in the early Paleogene, as survivors of the Cretaceous–Paleogene extinction event took advantage of empty ecological niches left behind by the extinction of the non-avian dinosaurs, pterosaurs, marine reptiles, and primitive fish groups. Mammals continued to diversify from relatively small, simple forms into

298-736: A divergent to convergent plate boundary. The Alpine Orogeny developed in response to the collision between the African and Eurasian plates during the closing of the Neotethys Ocean and the opening of the Central Atlantic Ocean. The result was a series of arcuate mountain ranges, from the Tell - Rif - Betic cordillera in the western Mediterranean through the Alps , Carpathians , Apennines , Dinarides and Hellenides to

447-465: A diverse group of large predatory marine reptiles, also became extinct. Fossil evidence indicates that squamates generally suffered very heavy losses in the K–Pg event, only recovering 10 million years after it. The extinction of Cretaceous lizards and snakes may have led to the evolution of modern groups such as iguanas, monitor lizards, and boas. The diversification of crown group snakes has been linked to

596-413: A few species of ground and water fowl, which radiated into all modern species of birds. Among other groups, teleost fish and perhaps lizards also radiated. The K–Pg extinction event was severe, global, rapid, and selective, eliminating a vast number of species. Based on marine fossils, it is estimated that 75% or more of all species became extinct. The event appears to have affected all continents at

745-531: A highly diverse group ranging from small-bodied forms to very large ones, radiating into multiple orders and colonizing the air and marine ecosystems by the Eocene . Birds , the only surviving group of dinosaurs, quickly diversified from the very few neognath and paleognath clades that survived the extinction event, also radiating into multiple orders, colonizing different ecosystems and achieving an extreme level of morphological diversity. Percomorph fish,

894-623: A land bridge formed across the Bering Straits between North America and Eurasia allowing the movement of land animals between the two continents. The PETM was followed by the less severe Eocene Thermal Maximum 2 (c. 53.69 Ma), and the Eocene Thermal Maximum 3 (c. 53 Ma). The early Eocene warm conditions were brought to an end by the Azolla event . This change of climate at about 48.5 Ma, is believed to have been caused by

1043-528: A lingering impact winter which halted photosynthesis in plants and plankton . The impact hypothesis, also known as the Alvarez hypothesis , was bolstered by the discovery of the 180 km (112 mi) Chicxulub crater in the Gulf of Mexico 's Yucatán Peninsula in the early 1990s, which provided conclusive evidence that the K–Pg boundary clay represented debris from an asteroid impact . The fact that

1192-534: A period in the earliest part of the Cenozoic of decreased acanthomorph diversity, although acanthomorphs diversified rapidly after the extinction. Teleost fish diversified explosively after the mass extinction, filling the niches left vacant by the extinction. Groups appearing in the Paleocene and Eocene epochs include billfish, tunas, eels, and flatfish. There is limited evidence for extinction of amphibians at

1341-419: A planktonic strategy of reproduction (numerous eggs and planktonic larvae), which would have been devastated by the K–Pg extinction event. Additional research has shown that subsequent to this elimination of ammonoids from the global biota, nautiloids began an evolutionary radiation into shell shapes and complexities theretofore known only from ammonoids. Approximately 35% of echinoderm genera became extinct at

1490-550: A proliferation of aquatic ferns from the genus Azolla , resulting in the sequestering of large amounts of CO 2 from the atmosphere by the plants. From this time until about 34 Ma, there was a slow cooling trend known as the Middle-Late Eocene Cooling. As temperatures dropped at high latitudes the presence of cold water diatoms suggests sea ice was able to form in winter in the Arctic Ocean, and by

1639-490: A range of different species provide definitive evidence for the persistence of archaic birds to within 300,000 years of the K–Pg boundary. The absence of these birds in the Paleogene is evidence that a mass extinction of archaic birds took place there. The most successful and dominant group of avialans , enantiornithes , were wiped out. Only a small fraction of ground and water-dwelling Cretaceous bird species survived

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1788-527: A result of cooling temperatures in the early Paleocene . Approximately 46% of diatom species survived the transition from the Cretaceous to the Upper Paleocene, a significant turnover in species but not a catastrophic extinction. The occurrence of planktonic foraminifera across the K–Pg boundary has been studied since the 1930s. Research spurred by the possibility of an impact event at

1937-919: A result, rather than a cause, of the plate tectonic forces that led to the propagation of rifting from the Central to the North Atlantic. Mountain building continued along the North America Cordillera in response to subduction of the Farallon plate beneath the North American Plate. Along the central section of the North American margin, crustal shortening of the Cretaceous to Paleocene Sevier Orogen lessened and deformation moved eastward. The decreasing dip of

2086-454: A small phylum of marine invertebrates, survived the K–Pg extinction event and diversified during the early Paleocene. The numbers bivalve genera exhibited significant diminution after the K–Pg boundary. Entire groups of bivalves, including rudists (reef-building clams) and inoceramids (giant relatives of modern scallops ), became extinct at the K–Pg boundary, with the gradual extinction of most inoceramid bivalves beginning well before

2235-502: Is associated with the Cretaceous–Paleogene extinction event. The boundary is defined as the rusty colored base of a 50 cm thick clay , which would have been deposited over only a few days. Similar layers are seen in marine and continental deposits worldwide. These layers include the iridium anomaly, microtektites , nickel -rich spinel crystals and shocked quartz , all indicators of a major extraterrestrial impact. The remains of

2384-476: Is clearly marked at the species level. Statistical analysis of marine losses at this time suggests that the decrease in diversity was caused more by a sharp increase in extinctions than by a decrease in speciation . Major spatial differences existed in calcareous nannoplankton diversity patterns; in the Southern Hemisphere, the extinction was less severe and recovery occurred much faster than in

2533-639: Is composed sediments scrapped from the descending Arabian Plate. From the Late Cretaceous, a volcanic arc developed on the Eurasia margin as the Neotethys crust was subducted beneath it. A separate intra-oceanic subduction zone in the Neotethys resulted in the obuction of ocean crust onto the Arabian margin in the Late Cretaceous to Paleocene, with break-off of the subducted oceanic plate close to

2682-537: Is estimated that 75% or more of all species on Earth vanished. However, the extinction also provided evolutionary opportunities: in its wake, many groups underwent remarkable adaptive radiation —sudden and prolific divergence into new forms and species within the disrupted and emptied ecological niches. Mammals in particular diversified in the Paleogene , evolving new forms such as horses , whales , bats , and primates . The surviving group of dinosaurs were avians,

2831-475: Is influenced by a lack of fossil records, rather than extinctions. Ostracods , a class of small crustaceans that were prevalent in the upper Maastrichtian, left fossil deposits in a variety of locations. A review of these fossils shows that ostracod diversity was lower in the Paleocene than any other time in the Cenozoic . Current research cannot ascertain whether the extinctions occurred prior to, or during,

2980-526: Is more common in asteroids than in the Earth's crust . As originally proposed in 1980 by a team of scientists led by Luis Alvarez and his son Walter , it is now generally thought that the K–Pg extinction was caused by the impact of a massive asteroid 10 to 15 km (6 to 9 mi) wide, 66 million years ago causing the Chicxulub crater , which devastated the global environment, mainly through

3129-681: Is no evidence for ice sheets at the poles during the Paleocene. The relatively cool conditions were brought to an end by the Thanetian Thermal Event, and the beginning of the PETM. This was one of the warmest times of the Phanerozoic eon, during which global mean surface temperatures increased to 31.6 °C. According to a study published in 2018, from about 56 to 48 Ma, annual air temperatures over land and at mid-latitude averaged about 23–29 °C (± 4.7 °C). For comparison, this

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3278-494: Is no evidence that late Maastrichtian non-avian dinosaurs could burrow, swim, or dive, which suggests they were unable to shelter themselves from the worst parts of any environmental stress that occurred at the K–Pg boundary. It is possible that small dinosaurs (other than birds) did survive, but they would have been deprived of food, as herbivorous dinosaurs would have found plant material scarce and carnivores would have quickly found prey in short supply. The growing consensus about

3427-451: Is postulated that some early monotremes, marsupials, and placentals were semiaquatic or burrowing, as there are multiple mammalian lineages with such habits today. Any burrowing or semiaquatic mammal would have had additional protection from K–Pg boundary environmental stresses. After the K–Pg extinction, mammals evolved to fill the niches left vacant by the dinosaurs. Some research indicates that mammals did not explosively diversify across

3576-472: Is thought that ammonites were the principal food of mosasaurs , a group of giant marine reptiles that became extinct at the boundary. The K–Pg extinction had a profound effect on the evolution of life on Earth . The elimination of dominant Cretaceous groups allowed other organisms to take their place, causing a remarkable amount of species diversification during the Paleogene Period. After

3725-474: Is thought that body sizes of placental mammalian survivors evolutionarily increased first, allowing them to fill niches after the extinctions, with brain sizes increasing later in the Eocene . Plant fossils illustrate the reduction in plant species across the K–Pg boundary. There is overwhelming evidence of global disruption of plant communities at the K–Pg boundary. Extinctions are seen both in studies of fossil pollen, and fossil leaves. In North America,

3874-456: The Afar mantle plume began to impact the base of the African lithosphere. Rifting across the southern Red Sea began in the mid Oligocene, and across the central and northern Red Sea regions in the late Oligocene and early Miocene. Climatic conditions varied considerably during the Paleogene. After the disruption of the Chicxulub impact settled, a period of cool and dry conditions continued from

4023-870: The Canadian Arctic Archipelago , Svalbard and northern Greenland resulting in the Eureka Orogeny . From c. 47 Ma, the eastern margin of Greenland was cut by the Reykjanes Ridge (the northeastern branch of the Mid-Atlantic Ridge) propagating northwards and splitting off the Jan Mayen microcontinent . After c. 33 Ma seafloor spreading in Labrador Sea and Baffin Bay gradually ceased and seafloor spreading focused along

4172-832: The Izu-Bonin-Mariana and Tonga-Kermadec arcs. Subduction of the Farallon Plate beneath the American plates continued from the Late Cretaceous. The Kula-Farallon spreading ridge lay to its north until the Eocene (c. 55 Ma), when the northern section of the plate split forming the Vancouver/Juan de Fuca Plate . In the Oligocene (c. 28 Ma), the first segment of the Pacific–Farallon spreading ridge entered

4321-448: The K–T extinction , was the 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 kg (55 lb) also became extinct, with the exception of some ectothermic species such as sea turtles and crocodilians . It marked

4470-629: The San Juan River in Colorado, indicate that the animal lived during the Cenozoic, approximately 64.5 Ma (about 1 million years after the K–Pg extinction event). If their existence past the K–Pg boundary can be confirmed, these hadrosaurids would be considered a dead clade walking . The scientific consensus is that these fossils were eroded from their original locations and then re-buried in much later sediments (also known as reworked fossils ). Most paleontologists regard birds as

4619-783: The Tasmanian Passage in the Eocene and deep ocean routes opening from the mid Oligocene. Rifting between the Antarctic Peninsula and the southern tip of South America formed the Drake Passage and opened the Southern Ocean also during this time, completing the breakup of Gondwana. The opening of these passages and the creation of the Southern Ocean established the Antarctic Circumpolar Current . Glaciers began to build across

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4768-666: The Taurides in the east. From the Late Cretaceous into the early Paleocene, Africa began to converge with Eurasia. The irregular outlines of the continental margins, including the Adriatic promontory (Adria) that extended north from the African Plate, led to the development of several short subduction zones, rather than one long system. In the western Mediterranean, the European Plate was subducted southwards beneath

4917-640: The group and the stage was made in the second half of the 20th century, when stratigraphers saw the need to distinguish between lithostratigraphic and chronostratigraphic names. The base of the Rupelian Stage (which is also the base of the Oligocene Series) is at the extinction of the foraminiferan genus Hantkenina . An official GSSP for the base of the Rupelian has been assigned in 1992 ( Massignano , Italy). The transition with

5066-458: The molluscan class Cephalopoda became extinct at the K–Pg boundary. These included the ecologically significant belemnoids , as well as the ammonoids , a group of highly diverse, numerous, and widely distributed shelled cephalopods. The extinction of belemnites enabled surviving cephalopod clades to fill their niches. Ammonite genera became extinct at or near the K–Pg boundary; there was a smaller and slower extinction of ammonite genera prior to

5215-451: The photic zone ) areas of the ocean were less impacted by the K–Pg boundary. Colonial coral species rely upon symbiosis with photosynthetic algae , which collapsed due to the events surrounding the K–Pg boundary, but the use of data from coral fossils to support K–Pg extinction and subsequent Paleocene recovery, must be weighed against the changes that occurred in coral ecosystems through the K–Pg boundary. Most species of brachiopods ,

5364-579: The African Plate, whilst in the eastern Mediterranean, Africa was subducted beneath Eurasia along a northward dipping subduction zone. Convergence between the Iberian and European plates led to the Pyrenean Orogeny and, as Adria pushed northwards the Alps and Carpathian orogens began to develop. The collision of Adria with Eurasia in the early Palaeocene was followed by a c.10 million year pause in

5513-575: The Antarctic at the beginning of the Oligocene. The Paleogene is divided into three series / epochs : the Paleocene, Eocene, and Oligocene. These stratigraphic units can be defined globally or regionally. For global stratigraphic correlation, the International Commission on Stratigraphy (ICS) ratify global stages based on a Global Boundary Stratotype Section and Point (GSSP) from a single formation (a stratotype ) identifying

5662-564: The Antarctica continent that now lay isolated in the south polar region and surrounded by cold ocean waters. These changes contributed to the fall in global temperatures and the beginning of icehouse conditions. Extensional stresses from the subduction zone along the northern Neotethys resulted in rifting between Africa and Arabia, forming the Gulf of Aden in the late Eocene. To the west, in the early Oligocene, flood basalts erupted across Ethiopia , northeast Sudan and southwest Yemen as

5811-545: The Arabian margin occurring during the Eocene. Continental collision began during the Eocene c. 35 Ma and continued into the Oligocene to c. 26 Ma. The Indian continent rifted from Madagascar at c. 83 Ma and drifted rapidly (c. 18 cm/yr in the Paleocene) northwards towards the southern margin of Eurasia. A rapid decrease in velocity to c. 5 cm/yr in the early Eocene records the collision of the Tethyan (Tibetan) Himalayas ,

5960-722: The Central Andes were dominated by the subduction of oceanic crust and the Southern Andes were impacted by the subduction of the Farallon-East Antarctic ocean ridge. The Caribbean Plate is largely composed of oceanic crust of the Caribbean Large Igneous Province that formed during the Late Cretaceous. During the Late Cretaceous to Paleocene, subduction of Atlantic crust was established along its northern margin, whilst to

6109-658: The Chattian has also been marked with a GSSP in August 2017 ( Monte Conero , Italy). The top of the Rupelian Stage (the base of the Chattian) is at the extinction of the foram genus Chiloguembelina (which is also the base of foram biozone P21b). The Rupelian overlaps the Orellan , Whitneyan and lower Arikareean North American Land Mammal Ages , the upper Mustersan and Tinguirirican South American Land Mammal Ages ,

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6258-547: The Cretaceous. Along with the aforementioned mosasaurs, plesiosaurs , represented by the families Elasmosauridae and Polycotylidae , became extinct during the event. The ichthyosaurs had disappeared from fossil record tens of millions of years prior to the K-Pg extinction event. Ten families of crocodilians or their close relatives are represented in the Maastrichtian fossil records, of which five died out prior to

6407-644: The Dinarides, Hellenides and Tauride mountain chains as the passive margin sediments of Adria were scrapped off onto the Eurasia crust during subduction. The Zagros mountain belt stretches for c. 2000 km from the eastern border of Iraq to the Makran coast in southern Iran . It formed as a result of the convergence and collision of the Arabian and Eurasian plates as the Neotethys Ocean closed and

6556-439: The Eocene ants became dominant and diverse, with larger colonies. Butterflies diversified as well, perhaps to take the place of leaf-eating insects wiped out by the extinction. The advanced mound-building termites, Termitidae , also appear to have risen in importance. There are fossil records of jawed fishes across the K–Pg boundary, which provide good evidence of extinction patterns of these classes of marine vertebrates. While

6705-608: The Farallon Plate beneath the western edge of South America continued from the Mesozoic. Over the Paleogene, changes in plate motion and episodes of regional slab shallowing and steepening resulted in variations in the magnitude of crustal shortening and amounts of magmatism along the length of the Andes . In the Northern Andes, an oceanic plateau with volcanic arc was accreted during the latest Cretaceous and Paleocene, whilst

6854-526: The Greenland and northwest European margins and is associated with the proto-Icelandic mantle plume , which rose beneath the Greenland lithosphere at c. 65 Ma. There were two main phases of volcanic activity with peaks at c. 60 Ma and c. 55 Ma. Magmatism in the British and Northwest Atlantic volcanic provinces occurred mainly in the early Palaeocene, the latter associated with an increased spreading rate in

7003-606: The Hell Creek Formation shows a minimum of 75% of turtle species survived. Following the extinction event, turtle diversity exceeded pre-extinction levels in the Danian of North America, although in South America it remained diminished. European turtles likewise recovered rapidly following the mass extinction. The rhynchocephalians which were a globally distributed and diverse group of lepidosaurians during

7152-413: The Himalayas in India through Myanmar ( West Burma block ) Sumatra , Java to West Sulawesi . During the Late Cretaceous to Paleogene, the northward movement of the Indian Plate led to the highly oblique subduction of the Neotethys along the edge of the West Burma block and the development of a major north-south transform fault along the margin of Southeast Asia to the south. Between c. 60 and 50 Ma,

7301-418: The India-Eurasia collision continued, movement of material away from the collision zone was accommodated along, and extended, the already existing major strike slip systems of the region. During the Paleocene, seafloor spreading along the Mid-Atlantic Ridge propagated from the Central Atlantic northwards between North America and Greenland in the Labrador Sea (c. 62 Ma) and Baffin Bay (c. 57 Ma), and, by

7450-421: The Jurassic and continued to diversify throughout the Cretaceous. They are currently the most successful and diverse group of living reptiles, with more than 10,000 extant species. The only major group of terrestrial lizards to go extinct at the end of the Cretaceous were the polyglyphanodontians , a diverse group of mainly herbivorous lizards known predominantly from the Northern Hemisphere. The mosasaurs ,

7599-429: The K-Pg boundary known as the Main Fossiliferous Layer (MFL) containing a thanatocoenosis of disarticulated vertebrate fossils, which was likely also caused by a catastrophic flood from the impact. The K–Pg boundary represents one of the most dramatic turnovers in the fossil record for various calcareous nanoplankton that formed the calcium deposits for which the Cretaceous is named. The turnover in this group

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7748-484: The K–Pg boundary subsequently becoming extinct in the Miocene . The gharial-like choristodere genus Champsosaurus ' palatal teeth suggest that there were dietary changes among the various species across the K–Pg event. More than 80% of Cretaceous turtle species passed through the K–Pg boundary. All six turtle families in existence at the end of the Cretaceous survived into the Paleogene and are represented by living species. Analysis of turtle survivorship in

7897-672: The K–Pg boundary resulted in numerous publications detailing planktonic foraminiferal extinction at the boundary; there is ongoing debate between groups which think the evidence indicates substantial extinction of these species at the K–Pg boundary, and those who think the evidence supports a gradual extinction through the boundary. There is strong evidence that local conditions heavily influenced diversity changes in planktonic foraminifera. Low and mid-latitude communities of planktonic foraminifera experienced high extinction rates, while high latitude faunas were relatively unaffected. Numerous species of benthic foraminifera became extinct during

8046-445: The K–Pg boundary, although taxa that thrived in low-latitude, shallow-water environments during the late Cretaceous had the highest extinction rate. Mid-latitude, deep-water echinoderms were much less affected at the K–Pg boundary. The pattern of extinction points to habitat loss, specifically the drowning of carbonate platforms , the shallow-water reefs in existence at that time, by the extinction event. Atelostomatans were affected by

8195-421: The K–Pg boundary, despite the ecological niches made available by the extinction of dinosaurs. Several mammalian orders have been interpreted as diversifying immediately after the K–Pg boundary, including Chiroptera ( bats ) and Cetartiodactyla (a diverse group that today includes whales and dolphins and even-toed ungulates ), although recent research concludes that only marsupial orders diversified soon after

8344-506: The K–Pg boundary. Deposit feeders were the most common bivalves in the catastrophe's aftermath. Abundance was not a factor that affected whether a bivalve taxon went extinct, according to evidence from North America. Veneroid bivalves developed deeper burrowing habitats as the recovery from the crisis ensued. Except for nautiloids (represented by the modern order Nautilida ) and coleoids (which had already diverged into modern octopodes , squids , and cuttlefish ) all other species of

8493-461: The K–Pg boundary. Five families have both Maastrichtian and Paleocene fossil representatives. All of the surviving families of crocodyliforms inhabited freshwater and terrestrial environments—except for the Dyrosauridae , which lived in freshwater and marine locations. Approximately 50% of crocodyliform representatives survived across the K–Pg boundary, the only apparent trend being that no large crocodiles survived. Crocodyliform survivability across

8642-412: The K–Pg boundary. However, morphological diversification rates among eutherians after the extinction event were thrice those of before it. Also significant, within the mammalian genera, new species were approximately 9.1% larger after the K–Pg boundary. After about 700,000 years, some mammals had reached 50 kilos (110 pounds), a 100-fold increase over the weight of those which survived the extinction. It

8791-439: The K–Pg boundary. A study of fossil vertebrates across the K–Pg boundary in Montana concluded that no species of amphibian became extinct. Yet there are several species of Maastrichtian amphibian, not included as part of this study, which are unknown from the Paleocene. These include the frog Theatonius lancensis and the albanerpetontid Albanerpeton galaktion ; therefore, some amphibians do seem to have become extinct at

8940-501: The K–Pg boundary. Long-term survival past the boundary was assured as a result of filling ecological niches left empty by extinction of non-avian dinosaurs. Based on molecular sequencing and fossil dating, many species of birds (the Neoaves group in particular) appeared to radiate after the K–Pg boundary. The open niche space and relative scarcity of predators following the K-Pg extinction allowed for adaptive radiation of various avian groups. Ratites , for example, rapidly diversified in

9089-418: The K–Pg event. Scientists agree that all non-avian dinosaurs became extinct at the K–Pg boundary. The dinosaur fossil record has been interpreted to show both a decline in diversity and no decline in diversity during the last few million years of the Cretaceous, and it may be that the quality of the dinosaur fossil record is simply not good enough to permit researchers to distinguish between the options. There

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9238-477: The K–Pg extinction event as marine environments were. Among the terrestrial clade Notosuchia , only the family Sebecidae survived; the exact reasons for this pattern are not known. Sebecids were large terrestrial predators, are known from the Eocene of Europe, and would survive in South America into the Miocene. Tethysuchians radiated explosively after the extinction event. Two families of pterosaurs, Azhdarchidae and Nyctosauridae , were definitely present in

9387-499: The K–Pg extinction event, although they suffered losses. In particular, metatherians largely disappeared from North America, and the Asian deltatheroidans became extinct (aside from the lineage leading to Gurbanodelta ). In the Hell Creek beds of North America, at least half of the ten known multituberculate species and all eleven metatherians species are not found above the boundary. Multituberculates in Europe and North America survived relatively unscathed and quickly bounced back in

9536-426: The K–Pg extinction event, biodiversity required substantial time to recover, despite the existence of abundant vacant ecological niches . Evidence from the Salamanca Formation suggests that biotic recovery was more rapid in the Southern Hemisphere than in the Northern Hemisphere. Despite the massive loss of life inferred to have occurred during the extinction, and a number of geologic formations worldwide that span

9685-425: The Labrador Sea, whilst northeast Atlantic magmatism occurred mainly during the early Eocene and is associated with a change in the spreading direction in the Labrador Sea and the northward drift of Greenland. The locations of the magmatism coincide with the intersection of propagating the rifts and large-scale, pre-existing lithospheric structures, which acted as channels to the surface for the magma . The arrival of

9834-463: The Late Cretaceous. At the Paleocene-Eocene boundary global temperatures rose rapidly with the onset of the Paleocene-Eocene Thermal Maximum (PETM). By the middle Eocene, temperatures began to drop again and by the late Eocene (c. 37 Ma) had decreased sufficiently for ice sheets to form in Antarctica. The global climate entered icehouse conditions at the Eocene-Oligocene boundary and the present day Late Cenozoic ice age began. The Paleogene began with

9983-482: The Lilliput effect. Insect damage to the fossilized leaves of flowering plants from fourteen sites in North America was used as a proxy for insect diversity across the K–Pg boundary and analyzed to determine the rate of extinction. Researchers found that Cretaceous sites, prior to the extinction event, had rich plant and insect-feeding diversity. During the early Paleocene, flora were relatively diverse with little predation from insects, even 1.7 million years after

10132-495: The Maastrichtian age, 28  shark families and 13 batoid families thrived, of which 25 and 9, respectively, survived the K–T boundary event. Forty-seven of all neoselachian genera cross the K–T boundary, with 85% being sharks. Batoids display with 15%, a comparably low survival rate. Among elasmobranchs, those species that inhabited higher latitudes and lived pelagic lifestyles were more likely to survive, whereas epibenthic lifestyles and durophagy were strongly associated with

10281-417: The Maastrichtian, and they likely became extinct at the K–Pg boundary. Several other pterosaur lineages may have been present during the Maastrichtian, such as the ornithocheirids , pteranodontids , a possible tapejarid , a possible thalassodromid and a basal toothed taxon of uncertain affinities, though they are represented by fragmentary remains that are difficult to assign to any given group. While this

10430-496: The Neotethys Ocean lying between it and southern Eurasia. Debate about the amount of deformation seen in the geological record in the India–Eurasia collision zone versus the size of Greater India, the timing and nature of the collision relative to the decrease in plate velocity, and explanations for the unusually high velocity of the Indian plate have led to several models for Greater India: 1) A Late Cretaceous to early Paleocene subduction zone may have lain between India and Eurasia in

10579-466: The Neotethys, dividing the region into two plates, subduction was followed by collision of India with Eurasia in the middle Eocene. In this model Greater India would have been less than 900 km wide; 2) Greater India may have formed a single plate, several thousand kilometres wide, with the Tethyan Himalaya microcontinent separated from the Indian continent by an oceanic basin . The microcontinent collided with southern Eurasia c. 58 Ma (late Paleocene), whilst

10728-604: The North American subduction zone near Baja California leading to major strike-slip movements and the formation of the San Andreas Fault . At the Paleogene-Neogene boundary, spreading ceased between the Pacific and Farallon plates and the Farallon Plate split again forming the present date Nazca and Cocos plates. The Kula Plate lay between Pacific Plate and North America. To the north and northwest it

10877-675: The Northern Hemisphere. Following the extinction, survivor communities dominated for several hundred thousand years. The North Pacific acted as a diversity hotspot from which later nannoplankton communities radiated as they replaced survivor faunas across the globe. The K–Pg boundary record of dinoflagellates is not so well understood, mainly because only microbial cysts provide a fossil record, and not all dinoflagellate species have cyst-forming stages, which likely causes diversity to be underestimated. Recent studies indicate that there were no major shifts in dinoflagellates through

11026-649: The Pacific Plate moved north. At c. 47 Ma, movement of the hotspot ceased and the Pacific Plate motion changed from northward to northwestward in response to the onset of subduction along its western margin. This resulted in a 60 degree bend in the seamount chain. Other seamount chains related to hotspots in the South Pacific show a similar change in orientation at this time. Slow seafloor spreading continued between Australia and East Antarctica. Shallow water channels probably developed south of Tasmania opening

11175-559: The Pacific, Farallon, Kula and Izanagi plates. The central Pacific Plate grew by seafloor spreading as the other three plates were subducted and broken up. In the southern Pacific, seafloor spreading continued from the Late Cretaceous across the Pacific–Antarctic, Pacific-Farallon and Farallon–Antarctic mid ocean ridges. The Izanagi-Pacific spreading ridge lay nearly parallel to the East Asian subduction zone and between 60–50 Ma

11324-447: The Paleocene, but Asian forms were devastated, never again to represent a significant component of mammalian fauna. A recent study indicates that metatherians suffered the heaviest losses at the K–Pg event, followed by multituberculates, while eutherians recovered the quickest. K–Pg boundary mammalian species were generally small, comparable in size to rats ; this small size would have helped them find shelter in protected environments. It

11473-580: The Paleogene, and lasted from 33.9 Ma to 23.03 Ma. It is divided into two stages: the Rupelian 33.9 Ma to 27.82 Ma; and, Chattian 27.82 - 23.03 Ma. The GSSP for the base of the Oligocene is at Massignano , near Ancona , Italy . The extinction the hantkeninid planktonic foraminifera is the key marker for the Eocene-Oligocene boundary, which was a time of climate cooling that led to widespread changes in fauna and flora. The final stages of

11622-533: The Tell, Rif, Betic and Apennine mountain chains. The rate of convergence was less than the subduction rate of the dense lithosphere of the western Mediterranean and roll-back of the subducting slab led to the arcuate structure of these mountain ranges. In the eastern Mediterranean, c. 35 Ma, the Anatolide-Tauride platform (northern part of Adria) began to enter the trench leading to the development of

11771-548: The adaptations of many dinosaurs to cold environments. Whether the extinction occurred gradually or suddenly has been debated, as both views have support from the fossil record. A highly informative sequence of dinosaur-bearing rocks from the K–Pg boundary is found in western North America, particularly the late Maastrichtian-age Hell Creek Formation of Montana . Comparison with the older Judith River Formation (Montana) and Dinosaur Park Formation ( Alberta ), which both date from approximately 75 Ma, provides information on

11920-609: The atmosphere, causing longer-term effects on the climate and food chain . In October 2019, researchers asserted that the event rapidly acidified the oceans and produced long-lasting effects on the climate, detailing the mechanisms of the mass extinction. Other causal or contributing factors to the extinction may have been the Deccan Traps and other volcanic eruptions, climate change , and sea level change. However, in January 2020, scientists reported that climate-modeling of

12069-489: The base of the Eocene is at Dababiya, near Luxor , Egypt and is marked by the start of a significant variation in global carbon isotope ratios, produced by a major period of global warming. The change in climate was due to a rapid release of frozen methane clathrates from seafloor sediments at the beginning of the Paleocene-Eocene thermal maximum (PETM). The Oligocene is the third and youngest series/epoch of

12218-402: The biotic recovery in the aftermath of the K-Pg extinction event. Pan-Gekkotans weathered the extinction event well, with multiple lineages likely surviving. ∆ Ca values indicate that prior to the mass extinction, marine reptiles at the top of food webs were feeding on only one source of calcium, suggesting their populations exhibited heightened vulnerability to extinctions at the terminus of

12367-402: The boundary associated with a late Cretaceous marine regression, and a small, gradual reduction in ammonite diversity occurred throughout the very late Cretaceous. Researchers have pointed out that the reproductive strategy of the surviving nautiloids, which rely upon few and larger eggs, played a role in outsurviving their ammonoid counterparts through the extinction event. The ammonoids utilized

12516-495: The boundary interval. Ostracods that were heavily sexually selected were more vulnerable to extinction, and ostracod sexual dimorphism was significantly rarer following the mass extinction. Among decapods , extinction patterns were highly heterogeneous and cannot be neatly attributed to any particular factor. Decapods that inhabited the Western Interior Seaway were especially hard-hit, while other regions of

12665-498: The boundary layer. There were blooms of the taxa Thoracosphaera operculata and Braarudosphaera bigelowii at the boundary. Radiolaria have left a geological record since at least the Ordovician times, and their mineral fossil skeletons can be tracked across the K–Pg boundary. There is no evidence of mass extinction of these organisms, and there is support for high productivity of these species in southern high latitudes as

12814-450: The boundary may have resulted from their aquatic niche and ability to burrow, which reduced susceptibility to negative environmental effects at the boundary. Jouve and colleagues suggested in 2008 that juvenile marine crocodyliforms lived in freshwater environments as do modern marine crocodile juveniles, which would have helped them survive where other marine reptiles became extinct; freshwater environments were not so strongly affected by

12963-780: The boundary, only a few fossil sites contain direct evidence of the mass mortality that occurred exactly at the K-Pg boundary. These include the Tanis site of the Hell Creek Formation in North Dakota , USA, which contains a high number of well-preserved fossils that appear to have buried in a catastrophic flood event that was likely caused by the impact. Another important site is the Hornerstown Formation in New Jersey , USA, which has prominent layer at

13112-418: The boundary. The relatively low levels of extinction seen among amphibians probably reflect the low extinction rates seen in freshwater animals. Following the mass extinction, frogs radiated substantially, with 88% of modern anuran diversity being traced back to three lineages of frogs that evolved after the cataclysm. The choristoderes (a group of semi-aquatic diapsids of uncertain position) survived across

13261-678: The breakup of Pangaea occurred during the Paleogene as Atlantic Ocean rifting and seafloor spreading extended northwards, separating the North America and Eurasian plates, and Australia and South America rifted from Antarctica , opening the Southern Ocean . Africa and India collided with Eurasia forming the Alpine-Himalayan mountain chains and the western margin of the Pacific Plate changed from

13410-662: The brief but intense " impact winter " caused by the Chicxulub impact , which was followed by an abrupt period of warming. After temperatures stabilised, the steady cooling and drying of the Late Cretaceous-Early Paleogene Cool Interval that had spanned the last two ages of the Late Cretaceous continued, with only the brief interruption of the Latest Danian Event (c. 62.2 Ma) when global temperatures rose. There

13559-487: The changes in dinosaur populations over the last 10 million years of the Cretaceous. These fossil beds are geographically limited, covering only part of one continent. The middle–late Campanian formations show a greater diversity of dinosaurs than any other single group of rocks. The late Maastrichtian rocks contain the largest members of several major clades: Tyrannosaurus , Ankylosaurus , Pachycephalosaurus , Triceratops , and Torosaurus , which suggests food

13708-438: The circumstances of food chain disruption previously mentioned, non-avian dinosaurs died out, while some crocodiles survived. In this context, the survival of other endothermic animals, such as some birds and mammals, could be due, among other reasons, to their smaller needs for food, related to their small size at the extinction epoch. Prolonged cold is unlikely to have been a reason for the extinction of non-avian dinosaurs given

13857-406: The cold circumpolar current. Dense polar waters sank into the deep oceans and moved northwards, reducing global ocean temperatures. This cooling may have occurred over less than 100,000 years and resulted in a widespread extinction in marine life. By the Eocene-Oligocene boundary, sediments deposited in the ocean from glaciers indicate the presence of an ice sheet in western Antarctica that extended to

14006-599: The convergence of Africa and Eurasia, connected with the onset of the opening of the North Atlantic Ocean as Greenland rifted from the Eurasian Plate in the Palaeocene. Convergence rates between Africa and Eurasia increased again in the early Eocene and the remaining oceanic basins between Adria and Europe closed. Between about 40 and 30 Ma, subduction began along the western Mediterranean arc of

14155-427: The cooler oceans also reduced moisture in the atmosphere and increased aridity. By the early Oligocene, the North American and Eurasian tropical and subtropical forests were replaced by dry woodlands and widespread grasslands. The Early Oligocene Glacial Maximum lasted for about 200,000 years, and the global mean surface temperature continued to decrease gradually during the Rupelian . A drop in global sea levels during

14304-701: The crater are found at Chicxulub on the Yucatan Peninsula in Mexico . The extinction of the non-avian dinosaurs , ammonites and dramatic changes in marine plankton and many other groups of organisms, are also used for correlation purposes. The Eocene is the second series/epoch of the Paleogene, and lasted from 56.0 Ma to 33.9 Ma. It is divided into four stages: the Ypresian 56.0 Ma to 47.8 Ma; Lutetian 47.8 Ma to 41.2 Ma; Bartonian 41.2 Ma to 37.71 Ma; and, Priabonian 37.71 Ma to 33.9 Ma. The GSSP for

14453-423: The data suggests massive devastation and mass extinction of plants at the K–Pg boundary sections, although there were substantial megafloral changes before the boundary. In North America, approximately 57% of plant species became extinct. In high southern hemisphere latitudes, such as New Zealand and Antarctica, the mass die-off of flora caused no significant turnover in species, but dramatic and short-term changes in

14602-498: The deep-sea realm was able to remain seemingly unaffected, there was an equal loss between the open marine apex predators and the durophagous demersal feeders on the continental shelf. Within cartilaginous fish , approximately 7 out of the 41 families of neoselachians (modern sharks , skates, and rays) disappeared after this event and batoids (skates and rays) lost nearly all the identifiable species, while more than 90% of teleost fish (bony fish) families survived. In

14751-578: The early Mesozoic , had begun to decline by the mid-Cretaceous, although they remained successful in the Late Cretaceous of southern South America . They are represented today by a single species, the tuatara ( Sphenodon punctatus ) found in New Zealand . Outside of New Zealand, one rhynchocephalian is known to have crossed the K-Pg boundary, Kawasphenodon peligrensis , known from the earliest Paleocene (Danian) of Patagonia. The order Squamata comprising lizards and snakes first diversified during

14900-677: The early Eocene (c. 54 Ma), into the northeastern Atlantic between Greenland and Eurasia. Extension between North America and Eurasia, also in the early Eocene, led to the opening of the Eurasian Basin across the Arctic, which was linked to the Baffin Bay Ridge and Mid-Atlantic Ridge to the south via major strike slip faults. From the Eocene and into the early Oligocene, Greenland acted as an independent plate moving northwards and rotating anticlockwise. This led to compression across

15049-422: The early Paleocene provided the food source to support large benthic foraminiferal assemblages, which are mainly detritus-feeding. Ultimate recovery of the benthic populations occurred over several stages lasting several hundred thousand years into the early Paleocene. There is significant variation in the fossil record as to the extinction rate of marine invertebrates across the K–Pg boundary. The apparent rate

15198-630: The early Paleogene and are believed to have convergently developed flightlessness at least three to six times, often fulfilling the niche space for large herbivores once occupied by non-avian dinosaurs. Mammalian species began diversifying approximately 30 million years prior to the K–Pg boundary. Diversification of mammals stalled across the boundary. All major Late Cretaceous mammalian lineages, including monotremes (egg-laying mammals), multituberculates , metatherians (which includes modern marsupials), eutherians (which includes modern placentals), meridiolestidans , and gondwanatheres survived

15347-579: The end of the Cretaceous and underwent sudden extinction after the Cretaceous–Paleogene extinction event. Alternatively, interpretation based on the fossil-bearing rocks along the Red Deer River in Alberta, Canada, supports the gradual extinction of non-avian dinosaurs; during the last 10 million years of the Cretaceous layers there, the number of dinosaur species seems to have decreased from about 45 to approximately 12. Other scientists have made

15496-527: The end of the Cretaceous period, and with it the Mesozoic era, while heralding the beginning of the current era, the Cenozoic . In the geologic record , the K–Pg event is marked by a thin layer of sediment called the K–Pg boundary, Fatkito boundary or K–T boundary , which can be found throughout the world in marine and terrestrial rocks. The boundary clay shows unusually high levels of the metal iridium , which

15645-405: The endothermy of dinosaurs (see dinosaur physiology ) helps to understand their full extinction in contrast with their close relatives, the crocodilians. Ectothermic ("cold-blooded") crocodiles have very limited needs for food (they can survive several months without eating), while endothermic ("warm-blooded") animals of similar size need much more food to sustain their faster metabolism. Thus, under

15794-422: The event's severity, there was significant variability in the rate of extinction between and within different clades . Species that depended on photosynthesis declined or became extinct as atmospheric particles blocked sunlight and reduced the solar energy reaching the ground. This plant extinction caused a major reshuffling of the dominant plant groups. Omnivores , insectivores , and carrion -eaters survived

15943-409: The event, presumably because they depend on organic debris for nutrients, while biomass in the ocean is thought to have decreased. As the marine microbiota recovered, it is thought that increased speciation of benthic foraminifera resulted from the increase in food sources. In some areas, such as Texas, benthic foraminifera show no sign of any major extinction event, however. Phytoplankton recovery in

16092-490: The extinction event favored the asteroid impact and not volcanism . A wide range of terrestrial species perished in the K–Pg extinction, the best-known being the non-avian dinosaurs, along with many mammals, birds, lizards, insects , plants, and all the pterosaurs . In the oceans, the K–Pg extinction killed off plesiosaurs and mosasaurs and devastated teleost fish, sharks , mollusks (especially ammonites , which became extinct), and many species of plankton. It

16241-449: The extinction event is best represented by the marked discrepancy between the rich and relatively abundant late-Maastrichtian pollen record and the post-boundary fern spike. Polyploidy appears to have enhanced the ability of flowering plants to survive the extinction, probably because the additional copies of the genome such plants possessed allowed them to more readily adapt to the rapidly changing environmental conditions that followed

16390-586: The extinction event, perhaps because of the increased availability of their food sources. Neither strictly herbivorous nor strictly carnivorous mammals seem to have survived. Rather, the surviving mammals and birds fed on insects , worms , and snails , which in turn fed on detritus (dead plant and animal matter). In stream communities and lake ecosystems , few animal groups became extinct, including large forms like crocodyliforms and champsosaurs , because such communities rely less directly on food from living plants, and more on detritus washed in from

16539-471: The extinction event. Studies of the size of the ichnotaxon Naktodemasis bowni , produced by either cicada nymphs or beetle larvae, over the course of the K-Pg transition show that the Lilliput effect occurred in terrestrial invertebrates thanks to the extinction event. The extinction event produced major changes in Paleogene insect communities. Many groups of ants were present in the Cretaceous, but in

16688-473: The extinctions occurred simultaneously provides strong evidence that they were caused by the asteroid. A 2016 drilling project into the Chicxulub peak ring confirmed that the peak ring comprised granite ejected within minutes from deep in the earth, but contained hardly any gypsum , the usual sulfate-containing sea floor rock in the region: the gypsum would have vaporized and dispersed as an aerosol into

16837-534: The greenhouse conditions. The initial rise in global temperatures was related to the intrusion of magmatic sills into organic-rich sediments during volcanic activity in the North Atlantic Igneous Province, between about 56 and 54 Ma, which rapidly released large amounts of greenhouse gases into the atmosphere. This warming led to melting of frozen methane hydrates on continental slopes adding further greenhouses gases. It also reduced

16986-467: The impact, giving rise to today's birds. The only bird group known for certain to have survived the K–Pg boundary is the Aves. Avians may have been able to survive the extinction as a result of their abilities to dive, swim, or seek shelter in water and marshlands. Many species of avians can build burrows, or nest in tree holes, or termite nests, all of which provided shelter from the environmental effects at

17135-471: The impact. Beyond extinction impacts, the event also caused more general changes of flora such as giving rise to neotropical rainforest biomes like the Amazonia , replacing species composition and structure of local forests during ~6 million years of recovery to former levels of plant diversity . Rupelian The Rupelian is, in the geologic timescale , the older of two ages or

17284-414: The land, protecting them from extinction. Modern crocodilians can live as scavengers and survive for months without food, and their young are small, grow slowly, and feed largely on invertebrates and dead organisms for their first few years. These characteristics have been linked to crocodilian survival at the end of the Cretaceous. Similar, but more complex patterns have been found in the oceans. Extinction

17433-493: The landscape for centuries after the event. In the sediments below the K–Pg boundary the dominant plant remains are angiosperm pollen grains, but the boundary layer contains little pollen and is dominated by fern spores. More usual pollen levels gradually resume above the boundary layer. This is reminiscent of areas blighted by modern volcanic eruptions, where the recovery is led by ferns, which are later replaced by larger angiosperm plants. In North American terrestrial sequences,

17582-519: The late Eocene (c. 37 Ma) there is evidence of glaciation in Antarctica. Changes in deep ocean currents, as Australia and South America moved away from Antarctica opening the Drake and Tasmanian passages, were responsible for the drop in global temperatures. The warm waters of the South Atlantic, Indian and South Pacific oceans extended southward into the opening Southern Ocean and became part of

17731-602: The leading edge of Greater India, with the Lhasa Terrane of Tibet (southern Eurasian margin), along the Indus-Yarling-Zangbo suture zone . To the south of this zone, the Himalaya are composed of metasedimentary rocks scraped off the now subducted Indian continental crust and mantle lithosphere as the collision progressed. Palaeomagnetic data place the present day Indian continent further south at

17880-533: The leading northeastern edge of Greater India collided with the West Burma block resulting in deformation and metamorphism . During the middle Eocene, north-dipping subduction resumed along the southern edge of Southeast Asia, from west Sumatra to West Sulawesi, as the Australian Plate drifted slowly northwards. Collision between India and the West Burma block was complete by the late Oligocene. As

18029-412: The likelihood of perishing during the extinction event. There is evidence of a mass extinction of bony fishes at a fossil site immediately above the K–Pg boundary layer on Seymour Island near Antarctica , apparently precipitated by the K–Pg extinction event; the marine and freshwater environments of fishes mitigated the environmental effects of the extinction event. The result was Patterson's Gap,

18178-490: The lower boundary of the stage. The Paleocene is the first series/epoch of the Paleogene and lasted from 66.0 Ma to 56.0 Ma. It is divided into three stages: the Danian 66.0 - 61.6 Ma; Selandian 61.6 - 59.2 Ma; and, Thanetian 59.2 - 56.0 Ma. The GSSP for the base of the Cenozoic, Paleogene and Paleocene is at Oued Djerfane, west of El Kef , Tunisia . It is marked by an iridium anomaly produced by an asteroid impact, and

18327-864: The lower of two stages of the Oligocene Epoch / Series . It spans the time between 33.9 and 27.82 Ma . It is preceded by the Priabonian Stage (part of the Eocene) and is followed by the Chattian Stage. The stage is named after the small river Rupel in Belgium, a tributary to the Scheldt . The Belgian Rupel Group derives its name from the same source. The name Rupelian was introduced in scientific literature by Belgian geologist André Hubert Dumont in 1850. The separation between

18476-463: The mid Oligocene indicates major growth of the Antarctic glacial ice sheet. In the Late Oligocene , global temperatures began to warm slightly, though they continued to be significantly lower than during the previous epochs of the Paleogene and polar ice remained. Cretaceous%E2%80%93Paleogene extinction event The Cretaceous–Paleogene ( K–Pg ) extinction event , also known as

18625-510: The most diverse group of vertebrates today, first appeared near the end of the Cretaceous but saw a very rapid radiation into their modern order and family-level diversity during the Paleogene, achieving a diverse array of morphologies. The Paleogene is marked by considerable changes in climate from the Paleocene–Eocene Thermal Maximum , through global cooling during the Eocene to the first appearance of permanent ice sheets in

18774-533: The northeast Atlantic. By the late Oligocene, the plate boundary between North America and Eurasia was established along the Mid-Atlantic Ridge, with Greenland attached to the North American plate again, and the Jan Mayen microcontinent part of the Eurasian Plate, where its remains now lie to the east and possibly beneath the southeast of Iceland. The North Atlantic Igneous Province stretches across

18923-444: The number of flowering plants. However, phylogenetic evidence shows no mass angiosperm extinction. Due to the wholesale destruction of plants at the K–Pg boundary, there was a proliferation of saprotrophic organisms, such as fungi , that do not require photosynthesis and use nutrients from decaying vegetation. The dominance of fungal species lasted only a few years while the atmosphere cleared and plenty of organic matter to feed on

19072-621: The ocean. The development of the circumpolar current led to changes in the oceans, which in turn reduced atmospheric CO 2 further. Increasing upwellings of cold water stimulated the productivity of phytoplankton , and the cooler waters reduced the rate of bacterial decay of organic matter and promoted the growth of methane hydrates in marine sediments. This created a positive feedback cycle where global cooling reduced atmospheric CO 2 and this reduction in CO 2 lead to changes which further lowered global temperatures. The decrease in evaporation from

19221-426: The only surviving dinosaurs (see Origin of birds ). It is thought that all non-avian theropods became extinct, including then-flourishing groups such as enantiornithines and hesperornithiforms . Several analyses of bird fossils show divergence of species prior to the K–Pg boundary, and that duck, chicken, and ratite bird relatives coexisted with non-avian dinosaurs. Large collections of bird fossils representing

19370-399: The proto-Iceland plume has been considered the driving mechanism for rifting in the North Atlantic. However, that rifting and initial seafloor spreading occurred prior to the arrival of the plume, large scale magmatism occurred at a distance to rifting, and that rifting propagated towards, rather than away from the plume, has led to the suggestion the plume and associated magmatism may have been

19519-535: The rate of burial of organic matter as higher temperatures accelerated the rate of bacterial decomposition which released CO 2 back into the oceans. The (relatively) sudden climatic changes associated with the PETM resulted in the extinction of some groups of fauna and flora and the rise of others. For example, with the warming of the Arctic Ocean, around 70% of deep sea foraminifera species went extinct, whilst on land many modern mammals, including primates , appeared. Fluctuating sea levels meant, during low stands,

19668-489: The relative abundance of plant groups. European flora was also less affected, most likely due to its distance from the site of the Chicxulub impact. In northern Alaska and the Anadyr-Koryak region of Russia, the flora was minimally impacted. Another line of evidence of a major floral extinction is that the divergence rate of subviral pathogens of angiosperms sharply decreased, which indicates an enormous reduction in

19817-494: The same assessment following their research. Several researchers support the existence of Paleocene non-avian dinosaurs . Evidence of this existence is based on the discovery of dinosaur remains in the Hell Creek Formation up to 1.3 m (4.3 ft) above and 40,000 years later than the K–Pg boundary. Pollen samples recovered near a fossilized hadrosaur femur recovered in the Ojo Alamo Sandstone at

19966-531: The same time. Non-avian dinosaurs , for example, are known from the Maastrichtian of North America, Europe , Asia, Africa , South America, and Antarctica , but are unknown from the Cenozoic anywhere in the world. Similarly, fossil pollen shows devastation of the plant communities in areas as far apart as New Mexico , Alaska , China , and New Zealand . Nevertheless, high latitudes appear to have been less strongly affected than low latitudes. Despite

20115-682: The southwest, an island arc collided with the northern Andes forming an east dipping subduction zone where Caribbean lithosphere was subducted beneath the South American margin. During the Eocene (c. 45 Ma), subduction of the Farallon Plate along the Central American subduction zone was (re)established. Subduction along the northern section of the Caribbean volcanic arc ceased as the Bahamas carbonate platform collided with Cuba and

20264-413: The spreading ridge began to be subducted. By c. 50 Ma, the Pacific Plate was no longer surrounded by spreading ridges, but had a subduction zone along its western edge. This changed the forces acting on the Pacific Plate and led to a major reorganisation of plate motions across the entire Pacific region. The resulting changes in stress between the Pacific and Philippine Sea plates initiated subduction along

20413-538: The subducting Farallon Plate led to a flat-slab segment that increased friction between this and the base of the North American Plate. The resulting Laramide Orogeny , which began the development of the Rocky Mountains , was a broad zone of thick-skinned deformation , with faults extending to mid-crustal depths and the uplift of basement rocks that lay to the east of the Sevier belt, and more than 700km from

20562-404: The time of collision and decrease in plate velocity, indicating the presence of a large region to the north of India that has now been subducted beneath the Eurasian Plate or incorporated into the mountain belt. This region, known as Greater India, formed by extension along the northern margin of India during the opening of the Neotethys. The Tethyan Himalaya block lay along its northern edge, with

20711-664: The trench. With the Laramide uplift the Western Interior Seaway was divided and then retreated. During the mid to late Eocene (50–35 Ma), plate convergence rates decreased and the dip of the Farallon slab began to steepen. Uplift ceased and the region largely levelled by erosion . By the Oligocene, convergence gave way to extension, rifting and widespread volcanism across the Laramide belt. Ocean-continent convergence accommodated by east dipping subduction zone of

20860-570: The uppermost Headonian , Suevian and lower Arvernian European Land Mammal Mega Zones (the Rupelian spans the Mammal Paleogene zones 21 through 24 and part of 25 ), and the lower Hsandgolian Asian Land Mammal Age . It is also coeval with the only regionally used upper Aldingan and lower Janjukian stages of Australia, the upper Refugian and lower Zemorrian stages of California and the lower Kiscellian Paratethys stage of Central and eastern Europe. Other regionally used alternatives include

21009-483: The velocity of the plate did not decrease until c. 50 Ma when subduction rates dropped as young, oceanic crust entered the subduction zone; 3) This model assigns older dates to parts of Greater India, which changes its paleogeographic position relative to Eurasia and creates a Greater India formed of extended continental crust 2000 - 3000 km wide. The Alpine-Himalayan Orogenic Belt in Southeast Asia extends from

21158-538: The world's oceans were refugia that increased chances of survival into the Palaeocene. Among retroplumid crabs, the genus Costacopluma was a notable survivor. Approximately 60% of late-Cretaceous scleractinian coral genera failed to cross the K–Pg boundary into the Paleocene. Further analysis of the coral extinctions shows that approximately 98% of colonial species, ones that inhabit warm, shallow tropical waters, became extinct. The solitary corals, which generally do not form reefs and inhabit colder and deeper (below

21307-585: Was 10 to 15 °C higher than the current annual mean temperatures in these areas. This rapid rise in global temperatures and intense greenhouse conditions were due to a sudden increase in levels of atmospheric carbon dioxide (CO 2 ) and other greenhouse gases . An accompanying rise in humidity is reflected in an increase in kaolinite in sediments, which forms by chemical weathering in hot, humid conditions. Tropical and subtropical forests flourished and extended into polar regions. Water vapour (a greenhouse gas) associated with these forests also contributed to

21456-623: Was being subducted beneath the Aleutian trench . Spreading between the Kula and Pacific and Farallon plates ceased c. 40 Ma and the Kula Plate became part of the Pacific Plate. The Hawaiian-Emperor seamount chain formed above the Hawaiian hotspot . Originally thought to be stationary within the mantle, the hotspot is now considered to have drifted south during the Paleocene to early Eocene, as

21605-527: Was more severe among animals living in the water column than among animals living on or in the sea floor. Animals in the water column are almost entirely dependent on primary production from living phytoplankton , while animals on the ocean floor always or sometimes feed on detritus. Coccolithophorids and mollusks (including ammonites , rudists , freshwater snails , and mussels ), and those organisms whose food chain included these shell builders, became extinct or suffered heavy losses. For example, it

21754-480: Was occurring, modern birds were undergoing diversification; traditionally it was thought that they replaced archaic birds and pterosaur groups, possibly due to direct competition, or they simply filled empty niches, but there is no correlation between pterosaur and avian diversities that are conclusive to a competition hypothesis, and small pterosaurs were present in the Late Cretaceous. At least some niches previously held by birds were reclaimed by pterosaurs prior to

21903-614: Was plentiful immediately prior to the extinction. A study of 29 fossil sites in Catalan Pyrenees of Europe in 2010 supports the view that dinosaurs there had great diversity until the asteroid impact, with more than 100 living species. More recent research indicates that this figure is obscured by taphonomic biases and the sparsity of the continental fossil record. The results of this study, which were based on estimated real global biodiversity, showed that between 628 and 1,078 non-avian dinosaur species were alive at

22052-428: Was present. Once the atmosphere cleared photosynthetic organisms returned – initially ferns and other ground-level plants. In some regions, the Paleocene recovery of plants began with recolonizations by fern species, represented as a fern spike in the geologic record; this same pattern of fern recolonization was observed after the 1980 Mount St. Helens eruption . Just two species of fern appear to have dominated

22201-553: Was replaced by strike-slip movements as a transform fault, extending from the Mid-Atlantic Ridge, connected with the northern boundary of the Caribbean Plate. Subduction now focused along the southern Caribbean arc ( Lesser Antilles ). By the Oligocene, the intra-oceanic Central American volcanic arc began to collide with northwestern South American. At the beginning of the Paleogene, the Pacific Ocean consisted of

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