Paleogene (K–Pg) extinction event,[a] also known as
Tertiary (K–T) extinction,[b] was a sudden mass
extinction of some three-quarters of the plant and animal species on
Earth, approximately 66 million years ago. With the
exception of some ectothermic species such as the leatherback sea
turtle and crocodiles, no tetrapods weighing more than 25 kilograms
(55 lb) survived. It marked the end of the
and with it, the entire
Mesozoic Era, opening the
Cenozoic Era that
In the geologic record, the K–Pg event is marked by a thin layer of
sediment called the K–Pg boundary, which can be found throughout the
world in marine and terrestrial rocks. The boundary clay shows high
levels of the metal iridium, which is rare in the Earth's crust, but
abundant in asteroids.
As originally proposed in 1980 by a team of scientists led by Luis
Alvarez and Walter Alvarez, it is now generally thought that the
K–Pg extinction was caused by the impact of a massive comet or
asteroid 10 to 15 km (6.2 to 9.3 mi) wide, 66 million
years ago, which devastated the global environment, mainly through
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-kilometre-wide
Chicxulub crater in the
Gulf of Mexico
Gulf of Mexico in the early
1990s, which provided conclusive evidence that the K–Pg boundary
clay represented debris from an asteroid impact. The fact that 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, and contained hardly
any gypsum, the usual sulfate-containing sea floor rock in the region:
this would have vaporized and dispersed as an aerosol into the
atmosphere, initiating longer-term effects on the climate and food
Other causal or contributing factors to the extinction may have been
Deccan Traps and other volcanic eruptions, climate change, and
sea level change.
A wide range of species perished in the K–Pg extinction, the
best-known being the non-avian dinosaurs. It also destroyed a plethora
of other terrestrial organisms, including certain mammals, pterosaurs,
birds, lizards, insects, and plants. In the
oceans, the K–Pg extinction killed off plesiosaurs and the giant
marine lizards (Mosasauridae) and devastated fish, sharks,
mollusks (especially ammonites, which became extinct), and many
species of plankton. It is estimated that 75% or more of all species
Earth vanished. Yet 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. Birds, fish, and
perhaps lizards also radiated.
2.1 Marine invertebrates
2.3 Terrestrial invertebrates
2.4 Terrestrial plants
2.7.5 Non-avian dinosaurs
3.1 North American fossils
3.2 Marine fossils
5 Chicxulub impact
5.1 Evidence for impact
5.2 Effects of impact
Chicxulub crater drilling project
6 Alternative hypotheses
6.1 Deccan Traps
6.2 Multiple impact event
Maastrichtian sea-level regression
6.4 Multiple causes
7 Recovery and radiation
8 See also
9 Notes and references
10 Further reading
11 External links
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 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. 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 the boundary layer.
Marine extinction intensity during the Phanerozoic
Millions of years ago
The blue graph shows the apparent percentage (not the absolute number)
of marine animal genera becoming extinct during any given time
interval. It does not represent all marine species, just those that
are readily fossilized. The labels of the traditional "Big Five"
extinction events and the more recently recognised End-Capitanian
extinction event are clickable hyperlinks; see
Extinction event for
more details. (source and image info)
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 were made extinct.
The event appears to have affected all continents at the same time.
Non-avian dinosaurs, for example, are known from the
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
Despite the event's severity, there was significant variability in the
rate of extinction between and within different clades.
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 the extinction event, perhaps because of the increased
availability of their food sources. No purely herbivorous or
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, few animal groups became extinct because such
communities rely less directly on food from living plants and more on
detritus washed in from the land, protecting them from extinction.
Similar, but more complex patterns have been found in the oceans.
Extinction was more severe among animals living in the water column
than among animals living on or in the 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 is thought that
ammonites were the principal food of mosasaurs, a group of giant
marine reptiles that became extinct at the boundary. The largest
air-breathing survivors of the event, crocodyliforms and champsosaurs,
were semi-aquatic and had access to detritus. 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.
After the K–Pg extinction event, biodiversity required substantial
time to recover, despite the existence of abundant vacant ecological
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 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 the
K–Pg boundary resulted in
numerous publications detailing planktonic foraminiferal extinction at
the boundary, however, there is ongoing debate between groups that
think the evidence indicates substantial extinction of these species
at the K–Pg boundary, and those who think the evidence supports
multiple extinctions and expansions through the boundary.
Numerous species of benthic foraminifera became extinct during 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, however, it is thought that increased speciation
of benthic foraminifera resulted from the increase in food
Phytoplankton recovery in the early
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.
Discoscaphites iris ammonite from the
Owl Creek Formation (Upper
Cretaceous), Owl Creek, Ripley, Mississippi
There is significant variation in the fossil record as to the
extinction rate of marine invertebrates across the K–Pg boundary.
The apparent rate is influenced by a lack of fossil records, rather
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, however, whether the extinctions occurred prior to, or
during, the boundary interval.
Approximately 60% of late-
Scleractinia 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 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, however, 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.
The numbers of cephalopod, echinoderm, and bivalve genera exhibited
significant diminution after the K–Pg boundary. Most species of
brachiopods, a small phylum of marine invertebrates, survived the
K–Pg extinction event and diversified during the early Paleocene.
Rudist bivalves from the Late
Cretaceous of the Omani Mountains,
United Arab Emirates. Scale bar is 10 mm
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 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.
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 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 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.
Other invertebrate groups, including rudists (reef-building clams) and
inoceramids (giant relatives of modern scallops), also became extinct
at the K–Pg boundary.
This article needs attention from an expert in Palaeontology or
Fish. The specific problem is: The paragraph on sharks and survival
through the K-T event simply does not make sense. It contradicts the
article on sharks, and self-contradicts. It also requires some
language cleanup. WikiProject Palaeontology or WikiProject Fish
may be able to help recruit an expert. (March 2017)
There are substantial fossil records of jawed fishes across the K–Pg
boundary, which provide good evidence of extinction patterns of these
classes of marine vertebrates. While 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
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
Maastrichtian age, 28 shark families and 13 batoid families
thrived, of which 25 and 9 respectively, survived the K-T boundary
event. 47 of all neoselachian genera cross the K/T boundary, with 85%
being sharks. Batoids display with 15% a comparably low survival
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, however, the marine and freshwater environments of fishes
mitigated environmental effects of the extinction event.
Insect damage to the fossilized leaves of flowering plants from
fourteen sites in North America were 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, however, flora were relatively diverse
with little predation from insects, even 1.7 million years after
the extinction event.
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, 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 the relative abundance of plant
groups. 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.
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
was present. Once the atmosphere cleared, photosynthetic organisms,
such as ferns and other plants, returned.
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 the
There is limited evidence for extinction of amphibians at 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 the boundary. The relatively low levels of
extinction seen among amphibians probably reflect the low extinction
rates seen in freshwater animals.
Kronosaurus Hunt by Dmitry Bogdanov, 2008 – Large marine reptiles,
including plesiosaurians such as these, became extinct at the end of
The choristoderes (semi-aquatic archosauromorphs) survived across the
K–Pg boundary but would die out in the early Miocene.
More than 80% of
Cretaceous turtle species passed through the K–Pg
boundary. Additionally, all six turtle families in existence at the
end of the
Cretaceous survived into the
Paleogene and are represented
by living species.
The living non-archosaurian reptile taxa, lepidosaurians (lizards and
tuataras), survived across the K–Pg boundary. Living lepidosaurs
include the tuataras (the only living rhynchocephalians) and the
The rhynchocephalians were a widespread and relatively successful
group of lepidosaurians during the early Mesozoic, but began to
decline by the mid-Cretaceous, although they were very successful in
Cretaceous of South America. They are represented today
by a single genus, located exclusively in New Zealand.
The order Squamata, which is represented today by lizards, including
snakes and amphisbaenians (worm lizards), radiated into various
ecological niches during the
Jurassic and was successful throughout
the Cretaceous. They survived through the
K–Pg boundary and are
currently the most successful and diverse group of living reptiles,
with more than 6,000 extant species. Many families of terrestrial
squamates became extinct at the boundary, such as monstersaurians and
polyglyphanodonts, and fossil evidence indicates they suffered very
heavy losses in the KT event, only recovering 10 million years after
it. Giant non-archosaurian aquatic reptiles such as mosasaurs and
plesiosaurs, which were the top marine predators of their time, became
extinct by the end of the Cretaceous. The ichthyosaurs had
disappeared from fossil records before the mass extinction occurred.
The archosaur clade includes two surviving groups, crocodilians and
birds, along with the various extinct groups of non-avian dinosaurs
Ten families of crocodilians or their close relatives are represented
Maastrichtian fossil records, of which five died out prior to
the K–Pg boundary. Five families have both
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 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 the
K–Pg extinction event as marine environments were.
The Choristodera, a generally crocodile-like group of uncertain
phylogeny (possibly archosaurian) also survived the event, only to
become extinct in the Miocene. Studies on Champsosaurus' palatal
teeth suggest that there were dietary changes among the various
species across the KT event.
One family of pterosaurs, Azhdarchidae, was definitely present in the
Maastrichtian, and it likely became extinct at the K–Pg boundary.
These large pterosaurs were the last representatives of a declining
group that contained ten families during the mid-Cretaceous. Several
other pterosaur lineages may have been present during the
Maastrichtian, such as the ornithocheirids, pteranodontids,
nyctosaurids, as well as, a possible tapejarid, though they are
represented by fragmentary remains that are difficult to assign to any
given group. While this 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. In fact, at least some niches
previously held by birds were reclaimed by pterosaurs prior to the KT
Most paleontologists regard birds as 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 a range
of different species provides 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. A small fraction of the
Cretaceous bird species survived the impact, giving rise to today's
birds. The only bird group known for certain to have survived
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 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
Tyrannosaurus was among the dinosaurs living on
Earth before the
Excluding a few controversial claims, 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 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 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 the circumstances of food chain disruption previously
mentioned, non-avian dinosaurs died, 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
Whether the extinction occurred gradually or suddenly has been
debated, as both views have support from the fossil record. 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 taphonomical biases,
however, 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 the end of the
Cretaceous and underwent sudden
extinction after the Cretaceous–
Paleogene extinction event.
Alternatively, interpretation based on the fossil-bearing rocks along
Red Deer River
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 the same assessment following their research.
Several researchers support the existence of
Evidence of this existence is based on the discovery of dinosaur
remains in the
Hell Creek Formation
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 the San Juan River in Colorado, indicate that
the animal lived during the Cenozoic, approximately
7015203546520000000♠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. Scientific consensus, however, is that these
fossils were eroded from their original locations and then re-buried
in much later sediments (also known as reworked fossils).
Cretaceous mammalian lineages, including monotremes
(egg-laying mammals), multituberculates, metatherians, eutherians,
dryolestoideans, and gondwanatheres survived the K–Pg
extinction event, although they suffered losses. In particular,
metatherians largely disappeared from North America, and the Asian
deltatheroidans became extinct. 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 the Palaeocene, but Asian forms
were decimated, never again to represent a significant component on
Mammalian species began diversifying approximately 30 million
years prior to the K–Pg boundary. Diversification of mammals stalled
across the boundary. Current research indicates that mammals did
not explosively diversify across the K–Pg boundary, despite the
environment 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 after the K–Pg
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. In addition, it 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
K–Pg boundary environmental stresses.
North American fossils
Hell Creek Formation
In North American terrestrial sequences, the extinction event is best
represented by the marked discrepancy between the rich and relatively
Maastrichtian palynomorph record and the post-boundary
At present the most informative sequence of dinosaur-bearing rocks in
the world from the
K–Pg boundary is found in western North America,
particularly the late Maastrichtian-age
Hell Creek Formation
Hell Creek Formation of
Montana. This formation, when compared with the older (approximately
75 Ma) Judith River/
Dinosaur Park Formations (from
Alberta respectively) provides information on the changes in dinosaur
populations over the last 10 million years of the Cretaceous.
These fossil beds are geographically limited, covering only part of
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 was plentiful immediately prior
to the extinction.
In addition to rich dinosaur fossils, there are also plant fossils
that illustrate the reduction in plant species across the K–Pg
boundary. 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
The mass extinction of marine plankton appears to have been abrupt and
right at the K–Pg boundary.
Ammonite genera became extinct at
or near the K–Pg boundary; however, there was a smaller and slower
extinction of ammonite genera prior to the boundary that was
associated with a late
Cretaceous marine regression. The gradual
extinction of most inoceramid bivalves began well before the K–Pg
boundary, and a small, gradual reduction in ammonite diversity
occurred throughout the very late Cretaceous.
Further analysis shows that several processes were in progress in the
Cretaceous seas and partially overlapped in time, then ended with
the abrupt mass extinction. The diversity of marine life
decreased when the climate near the K-T boundary increased in
temperature. The temperature increased about three to four degrees
very rapidly between 65.4 and 65.2 million years ago, which is around
the time of the extinction event. Not only did the climate temperature
increase, but the water temperature decreased causing a drastic
decrease in marine diversity.
The scientific consensus is that the asteroid impact at the K–Pg
boundary left megatsunami deposits and sediments around the area of
the Caribbean Sea and Gulf of Mexico, from the colossal waves created
by the impact. These deposits have been identified in the La Popa
basin in northeastern Mexico, platform carbonates in northeastern
Brazil, in Atlantic deep-sea sediments, and in the form of
the thickest-known layer of graded sand deposits, around 100m thick,
Chicxulub crater itself, directly above the shocked granite
The megatsunami has been estimated to be more than 100 metres
(330 ft) tall, as the asteroid fell in an area of relatively
shallow sea; in deep sea it would have been 4.6 kilometres
(2.9 mi) tall.
The length of time taken for the extinction to occur is a
controversial issue, because some theories about the extinction's
causes require a rapid extinction over a relatively short period (from
a few years to a few thousand years) while others require longer
periods. The issue is difficult to resolve because of the
Signor–Lipps effect; that is, the fossil record is so incomplete
that most extinct species probably died out long after the most recent
fossil that has been found. Scientists have also found very few
continuous beds of fossil-bearing rock that cover a time range from
several million years before the K–Pg extinction to a few million
years after it. The sedimentation rate and thickness of K-Pg clay
from three sites suggest short duration of event, perhaps less than
ten thousand years.
Main articles: Cretaceous–
Paleogene boundary, Alvarez hypothesis,
and Chicxulub crater
Evidence for impact
Location of Chicxulub crater, Mexico
In 1980, a team of researchers consisting of Nobel Prize–winning
physicist Luis Alvarez, his son geologist Walter Alvarez, and chemists
Frank Asaro and
Helen Michel discovered that sedimentary layers found
all over the world at the
Cretaceous–Paleogene boundary contain a
concentration of iridium many times greater than normal (30, 160, and
20 times in three sections originally studied).
Iridium is extremely
rare in Earth's crust because it is a siderophile element, and
therefore, most of it sank with the iron into Earth's core during
planetary differentiation. As iridium remains abundant in most
asteroids and comets, the Alvarez team suggested that an asteroid
Earth at the time of the K–Pg boundary. There were
earlier speculations on the possibility of an impact event, but this
was the first hard evidence.
K–Pg boundary exposure in Trinidad Lake State Park, in the Raton
Basin of Colorado, shows an abrupt change from dark- to light-colored
rock. White line added to mark the transition.
This hypothesis was viewed as radical when first proposed, but
additional evidence soon emerged. The boundary clay was found to be
full of minute spherules of rock, crystallized from droplets of molten
rock formed by the impact.
Shocked quartz and other minerals were
also identified in the K–Pg boundary. Shocked minerals
have their internal structure deformed, and are created by intense
pressures as in nuclear blasts and meteorite impacts. The
identification of giant tsunami beds along the Gulf Coast and the
Caribbean also provided evidence, and suggested that the impact
may have occurred nearby—as did the discovery that the K–Pg
boundary became thicker in the southern United States, with
meter-thick beds of debris occurring in northern New Mexico.
Radar topography reveals the 180 km –wide (112 mi) ring of
the Chicxulub Crater.
Further research identified the giant Chicxulub crater, buried under
Chicxulub on the coast of Yucatán, as the source of the K–Pg
boundary clay. Identified in 1990 based on work by geophysicist
Glen Penfield in 1978, the crater is oval, with an average diameter of
roughly 180 kilometres (110 mi), about the size calculated by the
Alvarez team. The discovery of the crater—a necessary
prediction of the impact hypothesis—provided conclusive evidence for
a K–Pg impact, and strengthened the hypothesis that it caused the
In a 2013 paper,
Paul Renne of the Berkeley Geochronology Center
reported that the date of the impact is
7001660430000000000♠66.043±0.011 million years ago, based on
argon–argon dating. He further posits that the mass extinction
occurred within 32,000 years of this date.
In 2007, it was proposed that the impactor belonged to the Baptistina
family of asteroids. This link has been doubted, though not
disproved, in part because of a lack of observations of the asteroid
and its family. It was recently discovered that 298 Baptistina
does not share the chemical signature of the K–Pg impactor.
Further, a 2011
Wide-field Infrared Survey Explorer
Wide-field Infrared Survey Explorer (WISE) study of
reflected light from the asteroids of the family estimated their
break-up at 80 Ma, giving them insufficient time to shift orbits
Earth by 66 Ma.
Effects of impact
In March 2010, an international panel of 41 scientists reviewed 20
years of scientific literature and endorsed the asteroid hypothesis,
specifically the Chicxulub impact, as the cause of the extinction,
ruling out other theories such as massive volcanism. They had
determined that a 10-to-15-kilometre (6.2 to 9.3 mi) asteroid
Earth at Chicxulub on Mexico's Yucatán Peninsula. The
collision would have released the same energy as 100 teratonnes of TNT
(420 ZJ), more than a billion times the energy of the atomic
bombings of Hiroshima and Nagasaki.
The Chicxulub impact caused a global catastrophe. Some of the
phenomena were brief occurrences immediately following the impact, but
there were also long-term geochemical and climatic disruptions that
devastated the ecology.
The reentry of ejecta into Earth's atmosphere would include a brief
(hours long) but intense pulse of infrared radiation, killing exposed
organisms. A paper in 2013 by a prominent modeler of nuclear
winter suggested that, based on the amount of soot in the global
debris layer, the entire terrestrial biosphere might have burned,
iimplying a global soot-cloud blocking out the sun and creating a
nuclear winter effect. This is debated, however, with opponents
arguing that local ferocious fires, probably limited to North America,
fall short of global firestorms. This disagreement is termed the
"Cretaceous-Palaeogene firestorm debate."
Aside from the hypothesized fire and/or nuclear winter effects, the
impact would have created a dust cloud that blocked sunlight for up to
a year, inhibiting photosynthesis. Further, the asteroid struck a
region of sulfur-rich carbonate rock, much of which was vaporized,
thereby injecting sulfuric acid aerosols into the stratosphere, which
might have reduced sunlight reaching the Earth's surface by more than
50%, and would have caused acid rain. The resulting
acidification of the oceans would kill many organisms that grow shells
of calcium carbonate. At Brazos section, the paleo-sea surface
temperature dropped as much as 7 °C for decades after the
impact. It would take at least ten years for such aerosols to
dissipate, and would account for the extinction of plants and
phytoplankton, and subsequently herbivores and their predators.
Creatures whose food chains were based on detritus would have a
reasonable chance of survival, however.
If widespread fires occurred, they would have increased the CO
2 content of the atmosphere and caused a temporary greenhouse effect
once the dust clouds and aerosol settled, and, this would have
exterminated the most vulnerable organisms that survived the period
immediately after the impact.
Although most paleontologists now agree that an asteroid did hit the
Earth at approximately the end of the Cretaceous, there is an ongoing
dispute whether the impact was the sole cause of the
In a 2016 study, a team from the Potsdam Institute for Climate Impact
Research announced that the main cause for mass extinction was a
severe drop in global temperatures caused by large amounts sulfuric
acid droplets in the atmosphere. Freezing temperatures lasted for at
least three years. The asteroid hit in an especially unfortunate
region, having a large amount of combustible hydrocarbons and
The river bed at the Moody Creek Mine, 7 Mile Creek / Waimatuku,
Dunollie, New Zealand contains evidence of a devastating event on
terrestrial plant communities at the Cretaceous-
confirming the severity and global nature of the event.
Chicxulub crater drilling project
Chicxulub crater and Cretaceous–
In 2016, a scientific drilling project obtained deep rock core samples
from the peak ring around the Chicxulub impact crater. The discoveries
confirmed that the rock comprising the peak ring had been shocked by
immense pressure and melted in just minutes from its usual state into
its present form. Unlike sea-floor deposits, the peak ring was made of
granite originating much deeper in the earth, which had been ejected
to the surface by the impact. Gypsum, a sulfate-containing rock
usually present in the shallow seabed of the region, had been almost
entirely removed, vaporized into the atmosphere. Further, the event
was immediately followed by a megatsunami (a massive movement of sea
waters) sufficient to lay down the largest known layer of sand
separated by grain size directly above the peak ring.
These findings strongly support the impact's role in the extinction
event. The impactor was large enough to create a 120-mile peak ring,
to melt, shock and eject deep granite, to create colossal water
movements, and to eject an immense quantity of vaporized rock and
sulfates into the atmosphere, where they would have persisted for a
long time. This worldwide dispersal of dust and sulfates would have
affected climate catastrophically, led to large temperature drops, and
devastated the food chain.
Though the concurrence of the end-
Cretaceous extinctions with the
Chicxulub asteroid impact strongly supports the impact hypothesis,
some scientists continue to suggest that other causes may have
contributed. In particular, volcanic eruptions, climate change, sea
level change, and other impact events have been suggested to play a
Main article: Deccan Traps
Before 2000, arguments that the
Deccan Traps flood basalts caused the
extinction were usually linked to the view that the extinction was
gradual, as the flood basalt events were thought to have started
around 68 Mya and lasted more than 2 million years. The most
recent evidence shows that the traps erupted over a period of 800,000
years spanning the K–Pg boundary, and therefore may be responsible
for the extinction and the delayed biotic recovery thereafter.
Deccan Traps could have caused extinction through several
mechanisms, including the release of dust and sulfuric aerosols into
the air, which might have blocked sunlight and thereby reduced
photosynthesis in plants. In addition, Deccan Trap volcanism might
have resulted in carbon dioxide emissions that increased the
greenhouse effect when the dust and aerosols cleared from the
In the years when the
Deccan Traps hypothesis was linked to a slower
extinction, Luis Alvarez (who died in 1988) replied that
paleontologists were being misled by sparse data. While his assertion
was not initially well-received, later intensive field studies of
fossil beds lent weight to his claim. Eventually, most paleontologists
began to accept the idea that the mass extinctions at the end of the
Cretaceous were largely or at least partly due to a massive Earth
Walter Alvarez acknowledged that other major changes may
have contributed to the extinctions.
Some geophysical models suggest a connection between the impact and
the Deccan Traps. These models, combined with high-precision
radiometric dating, suggest that the Chicxulub impact could have
triggered some of the largest Deccan eruptions, and could have
triggered eruptions at active volcanoes anywhere on Earth.
Multiple impact event
Other crater-like topographic features have also been proposed as
impact craters formed in connection with Cretaceous-Paleogene
extinction. This suggests the possibility of near-simultaneous
multiple impacts, perhaps from a fragmented asteroidal object similar
to the Shoemaker–Levy 9 impact with Jupiter. In addition to the
180 km (110 mi) Chicxulub Crater, there is the 24 km
Boltysh crater in Ukraine
(7015205660879200000♠65.17±0.64 Ma), the 20 km
Silverpit crater in the North Sea
(7015187767720000000♠59.5±14.5 Ma) possibly formed by bolide
impact, and the controversial and much larger 600 km
(370 mi) Shiva crater. Any other craters that might have formed
Tethys Ocean would have been obscured by the northward tectonic
drift of Africa and India.
Maastrichtian sea-level regression
There is clear evidence that sea levels fell in the final stage of the
Cretaceous by more than at any other time in the
Mesozoic era. In some
Maastrichtian stage rock layers from various parts of the world, the
later layers are terrestrial; earlier layers represent shorelines and
the earliest layers represent seabeds. These layers do not show the
tilting and distortion associated with mountain building, therefore
the likeliest explanation is a "regression", a drop in sea level.
There is no direct evidence for the cause of the regression, but the
currently accepted explanation is that the mid-ocean ridges became
less active and sank under their own weight.
A severe regression would have greatly reduced the continental shelf
area, the most species-rich part of the sea, and therefore could have
been enough to cause a marine mass extinction; however, this change
would not have sufficed to cause the extinction of the ammonites. The
regression would also have caused climate changes, partly by
disrupting winds and ocean currents and partly by reducing the Earth's
albedo and increasing global temperatures.
Marine regression also resulted in the loss of epeiric seas, such as
Western Interior Seaway
Western Interior Seaway of North America. The loss of these seas
greatly altered habitats, removing coastal plains that ten million
years before had been host to diverse communities such as are found in
rocks of the
Dinosaur Park Formation. Another consequence was an
expansion of freshwater environments, since continental runoff now had
longer distances to travel before reaching oceans. While this change
was favorable to freshwater vertebrates, those that prefer marine
environments, such as sharks, suffered.
Proponents of multiple causation view the suggested single causes as
either too small to produce the vast scale of the extinction, or not
likely to produce its observed taxonomic pattern. In a review
article, J. David Archibald and David E. Fastovsky discussed a
scenario combining three major postulated causes: volcanism, marine
regression, and extraterrestrial impact. In this scenario, terrestrial
and marine communities were stressed by the changes in, and loss of,
habitats. Dinosaurs, as the largest vertebrates, were the first
affected by environmental changes, and their diversity declined. At
the same time, particulate materials from volcanism cooled and dried
areas of the globe. Then an impact event occurred, causing collapses
in photosynthesis-based food chains, both in the already-stressed
terrestrial food chains and in the marine food chains.
Recent work led by Sierra Peterson at Seymour Island, Antarctica,
showed two separate extinction events near the Cretaceous-Paleogene
boundary, with one correlating to Deccan Trap volcanism and one
correlated with the Chicxulub impact. The team analyzed combined
extinction patterns using a new clumped isotope temperature record
from a hiatus-free, expanded K-Pg boundary section. They documented a
7.8±3.3 °C warming synchronous with the onset of Deccan Traps
volcanism and a second, smaller warming at the time of meteorite
impact. They suggest "Local warming may have been amplified due to
simultaneous disappearance of continental or sea ice. Intra-shell
variability indicates a possible reduction in seasonality after Deccan
eruptions began, continuing through the meteorite event. Species
Seymour Island occurred in two pulses that coincide with
the two observed warming events, directly linking the end-Cretaceous
extinction at this site to both volcanic and meteorite events via
Recovery and radiation
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, spurring a remarkable series of
adaptive radiations in the Paleogene. The most striking example is
the replacement of dinosaurs by mammals. After the K–Pg extinction,
mammals evolved rapidly to fill the niches left vacant by the
dinosaurs. Also significant, within the mammalian genera, new species
were approximately 9.1% larger after the K–Pg boundary.
Other groups also underwent major radiations. Based on molecular
sequencing and fossil dating,
Neoaves appeared to radiate after the
K–Pg boundary. They even produced giant, flightless forms,
such as the herbivorous
Gastornis and Dromornithidae, and the
predatory Phorusrhacidae. The extinction of
Cretaceous lizards and
snakes may have led to the radiation of modern groups such as iguanas,
monitor lizards, and boas. On land, giant boid and enormous
madtsoiid snakes appeared, and in the seas, giant sea snakes radiated.
Teleost fish diversified explosively, filling the niches left
vacant by the extinction. Groups appearing in the
Paleocene and Eocene
include billfish, tunas, eels, and flatfish. Major changes are also
Paleogene insect communities. Many groups of ants were present
in the Cretaceous, but in 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.
Climate across Cretaceous–
List of unconfirmed impact craters on
Earth – for unconfirmed
craters similar to or larger than Chicxulub
Silurian extinction events
Triassic extinction event
Timeline of Cretaceous-
Paleogene extinction event research
Jurassic extinction event
Notes and references
^ The abbreviation is derived from the juxtaposition of K, the common
abbreviation for the Cretaceous, which in turn originates from the
correspondent German term Kreide, and Pg, which is the abbreviation
for the Paleogene.
^ The former designation includes the term 'Tertiary' (abbreviated as
T), which is now discouraged as a formal geochronological unit by the
International Commission on Stratigraphy.
^ Ogg, James G.; Gradstein, F. M; Gradstein, Felix M. (2004). A
geologic time scale 2004. Cambridge, UK: Cambridge University Press.
ISBN 0-521-78142-6. CS1 maint: Uses authors parameter (link)
^ "International Chronostratigraphic Chart". International Commission
on Stratigraphy. 2015. Archived from the original on May 30, 2014.
Retrieved 29 April 2015.
^ a b c d Renne, Paul R.; Deino, Alan L.; Hilgen, Frederik J.; Kuiper,
Klaudia F.; Mark, Darren F.; Mitchell, William S.; Morgan, Leah E.;
Mundil, Roland; Smit, Jan (7 February 2013). "Time Scales of Critical
Events Around the Cretaceous-
Paleogene Boundary" (PDF). Science. 339
(6120): 684–687. Bibcode:2013Sci...339..684R.
doi:10.1126/science.1230492. PMID 23393261.
^ Fortey, Richard (1999). Life: A Natural History of the First Four
Billion Years of
Life on Earth. Vintage. pp. 238–260.
^ Muench, David; Muench, Marc; Gilders, Michelle A. (2000). Primal
Forces. Portland: Graphic Arts Center Publishing. p. 20.
^ Schulte, Peter (March 5, 2010). "The Chicxulub
Asteroid Impact and
Extinction at the Cretaceous-
Paleogene Boundary". Science.
American Association for the Advancement of Science. 327 (5970):
1214–1218. Bibcode:2010Sci...327.1214S. doi:10.1126/science.1177265.
JSTOR 40544375. PMID 20203042.
^ Sleep, Norman H.; Lowe, Donald R. (9 April 2014). "Scientists
reconstruct ancient impact that dwarfs dinosaur-extinction blast".
American Geophysical Union. Retrieved 30 December 2016.
^ Amos, Jonathan (15 May 2017). "
Dinosaur asteroid hit 'worst possible
place'". BBC News Online. Retrieved 16 March 2018.
^ a b Alvarez LW, Alvarez W, Asaro F, Michel HV (1980).
"Extraterrestrial cause for the Cretaceous–
Science. 208 (4448): 1095–1108. Bibcode:1980Sci...208.1095A.
doi:10.1126/science.208.4448.1095. PMID 17783054.
^ Vellekoop, J.; Sluijs, A.; Smit, J.; et al. (May 2014). "Rapid
short-term cooling following the Chicxulub impact at the
Paleogene boundary". Proc. Natl. Acad. Sci. U.S.A. 111
(21): 7537–41. Bibcode:2014PNAS..111.7537V.
doi:10.1073/pnas.1319253111. PMID 24821785.
^ a b Hildebrand, A. R.; Penfield, G. T.; et al. (1991). "Chicxulub
crater: a possible Cretaceous/
Tertiary boundary impact crater on the
Yucatán peninsula, Mexico". Geology. 19 (9): 867–871.
^ a b c Schulte, P.; et al. (5 March 2010). "The Chicxulub Asteroid
Impact and Mass
Extinction at the Cretaceous-
Science. 327 (5970): 1214–1218. Bibcode:2010Sci...327.1214S.
doi:10.1126/science.1177265. PMID 20203042.
^ Keller G (2012). "The Cretaceous–
Tertiary Mass Extinction,
Chicxulub Impact, and Deccan Volcanism.
Earth and Life". In Talent JA.
Earth and Life: Global Biodiversity,
Extinction Intervals and
Biogeographic Perturbations Through Time. Springer.
pp. 759–793. ISBN 978-90-481-3427-4.
^ a b c Longrich, Nicholas R.; Tokaryk, Tim; Field, Daniel J. (2011).
"Mass extinction of birds at the Cretaceous–
boundary". Proceedings of the National Academy of Sciences. 108 (37):
doi:10.1073/pnas.1110395108. PMC 3174646 .
^ a b c Longrich, N. R.; Bhullar, B.-A. S.; Gauthier, J. A. (December
2012). "Mass extinction of lizards and snakes at the
Paleogene boundary". Proc. Natl. Acad. Sci. U.S.A. 109
(52): 21396–401. Bibcode:2012PNAS..10921396L.
doi:10.1073/pnas.1211526110. PMC 3535637 .
^ Labandeira CC; Johnson KR; et al. (2002). "Preliminary assessment of
insect herbivory across the Cretaceous-
Tertiary boundary: major
extinction and minimum rebound". In Hartman JH; Johnson KR; Nichols
Hell Creek Formation
Hell Creek Formation and the Cretaceous-
Tertiary Boundary in
the Northern Great Plains: An Integrated Continental Record of the End
of the Cretaceous. Geological Society of America. pp. 297–327.
^ Rehan, Sandra M.; Leys, Remko; Schwarz, Michael P. (2013). "First
Evidence for a Massive
Extinction Event Affecting Bees Close to the
K-T Boundary". PLoS ONE. 8 (10): e76683. Bibcode:2013PLoSO...876683R.
doi:10.1371/journal.pone.0076683. ISSN 1932-6203.
PMC 3806776 . PMID 24194843.
^ a b c d e f g Nichols, D. J. and K. R. Johnson (2008). Plants and
the K–T Boundary. Cambridge, Cambridge University Press.
^ Friedman M (2009). "Ecomorphological selectivity among marine
teleost fishes during the end-
Cretaceous extinction". PNAS. 106 (13):
5218–5223. Bibcode:2009PNAS..106.5218F. doi:10.1073/pnas.0808468106.
PMC 2664034 . PMID 19276106.
^ a b Jablonski, D.; Chaloner, W. G. (1994). "Extinctions in the
fossil record (and discussion)". Philosophical Transactions of the
Royal Society of London, Series B. 344 (1307): 11–17.
^ a b Alroy J (1999). "The fossil record of North American Mammals:
evidence for a Palaeocene evolutionary radiation". Systematic Biology.
48 (1): 107–118. doi:10.1080/106351599260472.
^ a b Feduccia A (1995). "Explosive evolution in
Tertiary birds and
mammals". Science. 267 (5198): 637–638. Bibcode:1995Sci...267..637F.
doi:10.1126/science.267.5198.637. PMID 17745839.
^ a b Friedman M (2010). "Explosive morphological diversification of
spiny-finned teleost fishes in the aftermath of the end-Cretaceous
extinction". Proceedings of the Royal Society B. 277 (1688):
1675–1683. doi:10.1098/rspb.2009.2177. PMC 2871855 .
^ Pospichal JJ (1996). "
Calcareous nannofossils and clastic sediments
at the Cretaceous–
Tertiary boundary, northeastern Mexico". Geology.
24 (3): 255–258. Bibcode:1996Geo....24..255P.
^ Bown P (2005). "Selective calcareous nannoplankton survivorship at
Tertiary boundary". Geology. 33 (8): 653–656.
^ Bambach RK, Knoll AH, Wang SC; Knoll; Wang (2004). "Origination,
extinction, and mass depletions of marine diversity". Paleobiology. 30
ISSN 0094-8373. CS1 maint: Multiple names: authors list
^ a b c d e f g h i j k l m n o p MacLeod N; Rawson PF; Forey PL;
Banner FT; Boudagher-Fadel MK; Bown PR; Burnett JA; Chambers P; Culver
S; Evans SE; Jeffery C; Kaminski MA; Lord AR; Milner AC; Milner AR;
Morris N; Owen E; Rosen BR; Smith AB; Taylor PD; Urquhart E; Young JR
(1997). "The Cretaceous–
Tertiary biotic transition". Journal of the
Geological Society. 154 (2): 265–292.
^ Gedl P (2004). "
Dinoflagellate cyst record of the deep-sea
Tertiary boundary at Uzgru, Carpathian Mountains, Czech
Republic". Geological Society, London,
Special Publications. 230:
^ Weishampel, D. B., P. M. Barrett (2004). "
Dinosaur Distribution". In
David B Weishampel; Peter Dodson; Halszka Osmólska. The Dinosauria
(2nd ed.). Berkeley: University of California Press.
pp. 517–606. OCLC 441742117. CS1 maint: Uses authors
^ a b Wilf P, Johnson KR; Johnson (2004). "Land plant extinction at
the end of the Cretaceous: a quantitative analysis of the North Dakota
megafloral record". Paleobiology. 30 (3): 347–368.
^ a b Sheehan Peter M, Hansen Thor A; Hansen (1986). "
as a buffer to extinction at the end of the Cretaceous". Geology. 14
(10): 868–870. Bibcode:1986Geo....14..868S.
ISSN 0091-7613. Retrieved 2007-07-04.
^ Aberhan M, Weidemeyer S, Kieesling W, Scasso RA, Medina FA;
Weidemeyer; Kiessling; Scasso; Medina (2007). "Faunal evidence for
reduced productivity and uncoordinated recovery in Southern Hemisphere
Paleogene boundary sections". Geology. 35 (3): 227–230.
Bibcode:2007Geo....35..227A. doi:10.1130/G23197A.1. CS1 maint:
Multiple names: authors list (link)
^ Sheehan Peter M, Fastovsky DE; Fastovsky (1992). "Major extinctions
of land-dwelling vertebrates at the Cretaceous–
eastern Montana". Geology. 20 (6): 556–560.
^ Kauffman E (2004). "
Mosasaur Predation on Upper Cretaceous
Ammonites from the United States Pacific Coast".
PALAIOS. Society for
Sedimentary Geology. 19 (1): 96–100.
ISSN 0883-1351. Retrieved 2007-06-17.
^ MacLeod N (1998). "Impacts and marine invertebrate extinctions".
Geological Society, London,
Special Publications. 140 (1): 217–246.
^ Courtillot, V (1999). Evolutionary Catastrophes: The Science of Mass
Extinction. Cambridge University Press. p. 2.
^ Arenillas I, Arz JA, Molina E, Dupuis C (2000). "An independent test
of planktic foraminiferal turnover across the Cretaceous/Paleogene
(K/P) boundary at El Kef, Tunisia: catastrophic mass extinction and
possible survivorship". Micropaleontology. 46 (1): 31–49.
^ MacLeod, N (1996). Nature of the Cretaceous-
planktonic foraminiferal record: stratigraphic confidence intervals,
Signor–Lipps effect, and patterns of survivorship. In:
Tertiary Mass Extinctions: Biotic and Environmental
Changes (MacLeod N, Keller G, editors). WW Norton. pp. 85–138.
^ a b Keller G, Adatte T, Stinnesbeck W, Rebolledo-Vieyra, Fucugauchi
JU, Kramar U, Stüben D; Adatte; Stinnesbeck; Rebolledo-Vieyra;
Urrutia Fucugauchi; Kramar; Stüben (2004). "Chicxulub impact predates
the K–T boundary mass extinction". PNAS. 101 (11): 3753–3758.
PMC 374316 . PMID 15004276. CS1 maint: Multiple
names: authors list (link)
^ Galeotti S, Bellagamba M, Kaminski MA, Montanari A (2002). "Deep-sea
benthic foraminiferal recolonisation following a volcaniclastic event
in the lower Campanian of the Scaglia Rossa Formation (Umbria-Marche
Basin, central Italy)" (PDF). Marine Micropaleontology. 44: 57–76.
doi:10.1016/s0377-8398(01)00037-8. Retrieved 2007-08-19.
^ Kuhnt W, Collins ES; Collins (1996). "8.
Cretaceous to Paleogene
benthic foraminifers from the Iberia abyssal plain" (PDF). Proceedings
Ocean Drilling Program, Scientific Results. Proceedings of the
Ocean Drilling Program. 149: 203–216.
doi:10.2973/odp.proc.sr.149.254.1996. Retrieved 2007-08-19.
^ Coles, GP; Ayress MA; Whatley RC (1990). "A comparison of North
Atlantic and 20 Pacific deep-sea Ostracoda". In RC Whatley; C Maybury.
Ostracoda and global events. Chapman & Hall. pp. 287–305.
^ Brouwers EM, De Deckker P; Deckker (1993). "Late
Danian Ostracode Faunas from Northern Alaska: Reconstructions of
Environment and Paleogeography". PALAIOS. 8 (2): 140–154.
doi:10.2307/3515168. JSTOR 3515168.
^ Vescsei A, Moussavian E; Moussavian (1997). "
Paleocene reefs on the
Maiella Platform Margin, Italy: An example of the effects of the
cretaceous/tertiary boundary events on reefs and carbonate platforms".
Facies. 36 (1): 123–139. doi:10.1007/BF02536880.
^ Rosen BR, Turnšek D (1989). Jell A; Pickett JW, eds. "Extinction
patterns and biogeography of scleractinian corals across the
Tertiary boundary". Memoir of the Association of
Australasian Paleontology. Proceedings of the Fifth International
Symposium on Fossil Cnidaria including Archaeocyatha and
Spongiomorphs. Brisbane, Queensland (8): 355–370.
^ Ward PD, Kennedy WJ, MacLeod KG, Mount JF; Kennedy; MacLeod; Mount
Ammonite and inoceramid bivalve extinction patterns in
Tertiary boundary sections of the Biscay region
(southwestern France, northern Spain)". Geology. 19 (12): 1181–1184.
maint: Multiple names: authors list (link)
^ Harries PJ, Johnson KR, Cobban WA, Nichols DJ; Johnson; Cobban;
Nichols (2002). "Marine Cretaceous-
Tertiary boundary section in
southwestern South Dakota: Comment and Reply". Geology. 30 (10):
ISSN 0091-7613. CS1 maint: Multiple names: authors list
^ Neraudeau D, Thierry J, Moreau P (1997). "Variation in echinoid
biodiversity during the Cenomanian–early Turonian transgressive
episode in Charentes (France)". Bulletin de la Société Géologique
de France. 168: 51–61.
^ Raup DM, Jablonski D (1993). "Geography of end-
bivalve extinctions". Science. 260 (5110): 971–973.
^ MacLeod KG (1994). "
Extinction of Inoceramid Bivalves in
Maastrichtian Strata of the Bay of Biscay Region of France and Spain".
Journal of Paleontology. 68 (5): 1048–1066.
^ a b Kriwet, Jürgen; Benton, Michael J. (2004). "Neoselachian
(Chondrichthyes, Elasmobranchii) Diversity across the
Tertiary Boundary". Palaeogeography, Palaeoclimatology,
Palaeoecology. 214 (3): 181–194.
^ Patterson, C (1993). Osteichthyes: Teleostei. In: The Fossil Record
2 (Benton, MJ, editor). Springer. pp. 621–656.
^ Noubhani, Abdelmajid (2010). "The Selachians' Faunas of the Moroccan
Phosphate Deposits and the K-T Mass Extinctions". Historical Biology.
22: 71–77. doi:10.1080/08912961003707349.
^ Zinsmeister WJ (1 May 1998). "Discovery of fish mortality horizon at
the K–T boundary on Seymour Island: Re-evaluation of events at the
end of the Cretaceous". Journal of Paleontology. 72 (3): 556–571.
^ a b c d e f g Robertson DS, McKenna MC, Toon OB, Hope S, Lillegraven
JA; McKenna; Toon; Hope; Lillegraven (2004). "Survival in the first
hours of the Cenozoic" (PDF). GSA Bulletin. 116 (5–6): 760–768.
Bibcode:2004GSAB..116..760R. doi:10.1130/B25402.1. Retrieved
2016-01-06. CS1 maint: Multiple names: authors list (link)
^ a b Labandeira Conrad C, Johnson Kirk R, Wilf Peter; Johnson; Wilf
(2002). "Impact of the terminal
Cretaceous event on plant–insect
associations" (PDF). Proceedings of the National Academy of Sciences
of the United States of America. 99 (4): 2061–2066.
PMC 122319 . PMID 11854501. CS1 maint: Multiple
names: authors list (link)
^ Wilf P, Labandeira CC, Johnson KR, Ellis B; Labandeira; Johnson;
Ellis (2006). "Decoupled
Insect Diversity After the
Cretaceous Extinction". Science. 313 (5790): 1112–1115.
PMID 16931760. CS1 maint: Multiple names: authors list
^ a b c Vajda Vivi, Raine J Ian, Hollis Christopher J; Raine; Hollis
(2001). "Indication of Global Deforestation at the
Tertiary Boundary by New Zealand Fern Spike". Science.
294 (5547): 1700–1702. Bibcode:2001Sci...294.1700V.
doi:10.1126/science.1064706. PMID 11721051. CS1 maint:
Multiple names: authors list (link)
^ Wilf, P.; Johnson, K. R. (2004). "Land plant extinction at the end
of the Cretaceous: a quantitative analysis of the North Dakota
megafloral record". Paleobiology. 30 (3): 347–368.
^ Johnson, KR; Hickey LJ (1991). Megafloral change across the
Tertiary boundary in the northern Great Plains and Rocky
Mountains. In: Global Catastrophes in
Earth History: An
Interdisciplinary Conference on Impacts, Volcanism, and Mass
Mortality, Sharpton VI and Ward PD (editors). Geological Society of
America. ISBN 978-0-8137-2247-4.
^ Askin, RA; Jacobson SR (1996). Palynological change across the
Tertiary boundary on Seymour Island, Antarctica:
environmental and depositional factors. In: Cretaceous–
Extinctions: Biotic and Environmental Changes, Keller G, MacLeod N
(editors). WW Norton. ISBN 978-0-393-96657-2.
^ Schultz PH, D'Hondt S; d'Hondt (1996). "Cretaceous–Tertiary
(Chicxulub) impact angle and its consequences". Geology. 24 (11):
^ Vajda V, McLoughlin S; McLoughlin (2004). "Fungal Proliferation at
Tertiary Boundary" (PDF). Science. 303 (5663):
1489–1490. doi:10.1126/science.1093807. PMID 15001770. Archived
from the original (PDF) on 2007-09-26. Retrieved 2007-07-07.
^ Fawcett, J. A.; Maere, S.; Van de Peer, Y. (April 2009). "Plants
with double genomes might have had a better chance to survive the
Tertiary extinction event". Proceedings of the National
Academy of Sciences of the United States of America. 106 (14):
5737–5742. Bibcode:2009PNAS..106.5737F. doi:10.1073/pnas.0900906106.
ISSN 0027-8424. PMC 2667025 . PMID 19325131.
^ Archibald JD, Bryant LJ (1990). "Differential Cretaceous–Tertiary
extinction of nonmarine vertebrates; evidence from northeastern
Montana". In Sharpton VL, Ward PD. Global Catastrophes in Earth
History: an Interdisciplinary Conference on Impacts, Volcanism, and
Mass Mortality. Geological Society of America,
Special Paper. 247.
pp. 549–562. doi:10.1130/spe247-p549.
ISBN 0-8137-2247-0. CS1 maint: Uses authors parameter (link)
CS1 maint: Uses editors parameter (link)
^ Estes, R (1964). "Fossil vertebrates from the Late
Formation, Eastern Wyoming". University of California Publications,
Department of Geological Sciences. 49: 1–180.
^ Gardner J. D. (2000). "Albanerpetontid amphibians from the Upper
Cretaceous (Campanian and Maastrichtian) of North America".
Geodiversitas. 22 (3): 349–388.
^ Sheehan P. M., Fastovsky D. E.; Fastovsky (1992). "Major extinctions
of land-dwelling vertebrates at the Cretaceous-
Eastern Montana". Geology. 20 (6): 556–560.
^ Novacek MJ (1999). "100 Million Years of Land Vertebrate
Evolution: The Cretaceous-Early
Tertiary Transition". Annals of the
Missouri Botanical Garden. 86 (2): 230–258. doi:10.2307/2666178.
^ Apesteguía Sebastián; Novas Fernando E (2003). "Large Cretaceous
sphenodontian from Patagonia provides insight into lepidosaur
evolution in Gondwana". Nature. 425 (6958): 609–612.
^ Lutz, D (2005). Tuatara: A Living Fossil. DIMI Press.
^ Longrich, Nicholas R.; Bhullar, Bhart-Anjan S.; Gauthier, Jacques A.
(2012). "Mass extinction of lizards and snakes at the
Paleogene boundary". Proceedings of the National Academy
of Sciences of the United States of America. 109 (52): 21396–401.
PMC 3535637 . PMID 23236177. Retrieved December 11,
^ Chatterjee S, Small BJ; Small (1989). "New plesiosaurs from the
Cretaceous of Antarctica". Geological Society, London, Special
Publications. 47 (1): 197–215. Bibcode:1989GSLSP..47..197C.
doi:10.1144/GSL.SP.1989.047.01.15. Retrieved 2007-07-04.
^ O'Keefe FR (2001). "A cladistic analysis and taxonomic revision of
Plesiosauria (Reptilia: Sauropterygia)". Acta Zoologica Fennica.
^ "The Great
Archosaur Lineage". University of California Museum of
Paleontology. Retrieved 2014-12-18.
^ Brochu CA (2004). "Calibration age and quartet divergence date
estimation". Evolution. 58 (6): 1375–1382. doi:10.1554/03-509.
^ Jouve S, Bardet, N, Jalil N-E, Suberbiola XP, Bouya B, Amaghzaz M;
Bardet; Jalil; Suberbiola; Bouya; Amaghzaz (2008). "The oldest African
crocodylian: phylogeny, paleobiogeography, and differential
survivorship of marine reptiles through the Cretaceous-Tertiary
Boundary". Journal of Vertebrate Paleontology. 28 (2): 409–421.
ISSN 0272-4634. CS1 maint: Multiple names: authors list
^ Evans, Susan E.; Klembara, Jozef (2005). "A choristoderan reptile
(Reptilia: Diapsida) from the Lower
Miocene of northwest Bohemia
(Czech Republic)". Journal of Vertebrate Paleontology. 25 (1):
^ Morphology and function of the palatal dentition in Choristodera
Journal of Anatomy 228(3):n/a-n/a · November 2015
^ Company J.; Ruiz-Omeñaca J. I.; Pereda Suberbiola X. (1999). "A
long-necked pterosaur (Pterodactyloidea, Azhdarchidae) from the Upper
Cretaceous of Valencia, Spain". Geologie en Mijnbouw. 78 (3):
^ Barrett P. M.; Butler R. J.; Edwards N. P.; Milner A. R. (2008).
Pterosaur distribution in time and space: an atlas" (PDF).
Zitteliana. 28: 61–107.
^ Slack KE, Jones CM, Ando T, Harrison GL, Fordyce RE, Arnason U,
Penny D; Jones; Ando; Harrison; Fordyce; Arnason; Penny (2006). "Early
Penguin Fossils, Plus Mitochondrial Genomes, Calibrate Avian
Evolution". Molecular Biology and Evolution. 23 (6): 1144–1155.
doi:10.1093/molbev/msj124. PMID 16533822. CS1 maint:
Multiple names: authors list (link)
^ Penny D, Phillips MJ; Phillips (2004). "The rise of birds and
mammals: are microevolutionary processes sufficient for
macroevolution". Trends Ecol Evol. 19 (10): 516–522.
doi:10.1016/j.tree.2004.07.015. PMID 16701316.
^ Butler Richard J.; Barrett Paul M.; Nowbath Stephen; Upchurch Paul
(2009). "Estimating the effects of sampling biases on pterosaur
diversity patterns: implications for hypotheses of bird/pterosaur
competitive replacement". Paleobiology. 35 (3): 432–446.
^ Prondvai E.; Bodor E. R.; Ösi A. (2014). "Does morphology reflect
osteohistology-based ontogeny? A case study of Late Cretaceous
pterosaur jaw symphyses from Hungary reveals hidden taxonomic
diversity". Paleobiology. 40 (2): 288–321. doi:10.1666/13030.
^ Longrich, N. R.; Martill, D. M.; Andres, B. (2018). "Late
Maastrichtian pterosaurs from North Africa and mass extinction of
Pterosauria at the Cretaceous-
Paleogene boundary". PLoS Biology. 16
(3): e2001663. doi:10.1371/journal.pbio.2001663.
^ Hou L, Martin M, Zhou Z, Feduccia A; Martin; Zhou; Feduccia (1996).
"Early Adaptive Radiation of Birds: Evidence from Fossils from
Northeastern China". Science. 274 (5290): 1164–1167.
PMID 8895459. CS1 maint: Multiple names: authors list (link)
^ Clarke JA, Tambussi CP, Noriega JI, Erickson GM, Ketcham RA;
Tambussi; Noriega; Erickson; Ketcham (2005). "Definitive fossil
evidence for the extant avian radiation in the Cretaceous". Nature.
433 (7023): 305–308. Bibcode:2005Natur.433..305C.
doi:10.1038/nature03150. PMID 15662422. CS1 maint: Multiple
names: authors list (link)
^ "Primitive Birds Shared Dinosaurs' Fate". Science Daily. 20
September 2011. Retrieved 20 September 2011.
^ a b c d e David, Archibald; David Fastovsky (2004). "Dinosaur
Extinction" (PDF). In Weishampel David B; Dodson Peter; Osmólska
Dinosauria (2nd ed.). Berkeley: University of California
Press. pp. 672–684. ISBN 0-520-24209-2.
^ a b Ocampo, A; Vajda V; Buffetaut E (2006). "Unravelling the
Paleogene (K–T) turnover, evidence from flora, fauna
and geology in biological processes associated with impact events". In
Cockell C; Gilmour I; Koeberl C. Biological Processes Associated with
Impact Events. SpringerLink. pp. 197–219.
^ Rieraa V, Marmib J, Omsa O, Gomez B; Marmi; Oms; Gomez (March 2010).
"Orientated plant fragments revealing tidal palaeocurrents in the
Fumanya mudflat (Maastrichtian, southern Pyrenees): Insights in
palaeogeographic reconstructions". Palaeogeography, Palaeoclimatology,
Palaeoecology. 288 (1–4): 82–92.
doi:10.1016/j.palaeo.2010.01.037. CS1 maint: Multiple names:
authors list (link)
^ Loeuff Le J (2012). "Paleobiogeography and biodiversity of Late
Maastrichtian dinosaurs: how many dinosaur species became extinct at
Tertiary boundary?". Bulletin de la Société
Géologique de France. 183 (6): 547–559.
^ Ryan MJ, Russell AP, Eberth DA, Currie PJ; Russell; Eberth; Currie
(2001). "The taphonomy of a Centrosaurus (Ornithischia: Ceratopsidae)
bone bed from the
Dinosaur Park Formation (Upper Campanian), Alberta,
Canada, with comments on cranial ontogeny" (PDF). PALAIOS. 16 (5):
Archived from the original (PDF) on 2009-07-20. CS1 maint:
Multiple names: authors list (link)
^ Sloan RE, Rigby K, Van Valen LM, Gabriel Diane; Rigby; Van Valen;
Gabriel (1986). "Gradual dinosaur extinction and simultaneous ungulate
radiation in the Hell Creek formation". Science. 232 (4750):
doi:10.1126/science.232.4750.629. PMID 17781415. Retrieved
2007-05-18. CS1 maint: Multiple names: authors list (link)
^ Fassett JE, Lucas SG, Zielinski RA, Budahn JR; Lucas; Zielinski;
Budahn (2001). "Compelling new evidence for
Paleocene dinosaurs in the
Ojo Alamo Sandstone San Juan Basin, New
Mexico and Colorado, USA"
(PDF). International Conference on Catastrophic Events and Mass
Extinctions: Impacts and Beyond, 9–12 July 2000, Vienna, Austria.
1053: 45–46. Bibcode:2001caev.conf.3139F. Retrieved
2007-05-18. CS1 maint: Multiple names: authors list (link)
^ Sullivan RM (2003). "No
Paleocene dinosaurs in the San Juan Basin,
New Mexico". Geological Society of America Abstracts with Programs. 35
(5): 15. Retrieved 2007-07-02.
^ Gelfo JN, Pascual R (2001). "Peligrotherium tropicalis (Mammalia,
Dryolestida) from the early
Paleocene of Patagonia, a survival from a
Mesozoic Gondwanan radiation" (PDF). Geodiversitas. 23: 369–379.
Archived from the original (PDF) on 2012-02-12.
^ Goin FJ, Reguero MA, Pascual R, von Koenigswald W, Woodburne MO,
Case JA, Marenssi SA, Vieytes C, Vizcaíno SF (2006). "First
gondwanatherian mammal from Antarctica". Geological Society, London,
Special Publications. 258: 135–144. Bibcode:2006GSLSP.258..135G.
doi:10.1144/GSL.SP.2006.258.01.10. CS1 maint: Uses authors
^ McKenna, MC; Bell SK (1997). Classification of mammals: above the
species level. Columbia University Press.
^ Wood, D. Joseph (2010). The
Extinction of the Multituberculates
Outside North America: a Global Approach to Testing the Competition
Model (M.S.). The Ohio State University.
^ a b Bininda-Emonds OR, Cardillo M, Jones KE, MacPhee RD, Beck RM,
Grenyer R, Price SA, Vos RA, Gittleman JL, Purvis A (2007). "The
delayed rise of present-day mammals" (PDF). Nature. 446 (7135):
507–512. Bibcode:2007Natur.446..507B. doi:10.1038/nature05634.
^ a b Springer MS, Murphy WJ, Eizirik E, O'Brien SJ (2003). "Placental
mammal diversification and the Cretaceous–
Tertiary boundary" (PDF).
PNAS. 100 (3): 1056–1061. Bibcode:2003PNAS..100.1056S.
doi:10.1073/pnas.0334222100. PMC 298725 .
^ Dodson, Peter (1996). The Horned Dinosaurs: A Natural History.
Princeton: Princeton University Press. pp. 279–281.
^ "Online guide to the continental Cretaceous–
Tertiary boundary in
the Raton basin,
Colorado and New Mexico". U.S. Geological Survey.
2004. Archived from the original on 2006-09-25. Retrieved
^ Smathers, GA; Mueller-Dombois D (1974). Invasion and Recovery of
Vegetation after a Volcanic Eruption in Hawaii, Scientific Monograph
Number 5. United States National Park Service. Retrieved
^ a b c d Pope KO, D'Hondt SL, Marshall CR (1998). "Meteorite impact
and the mass extinction of species at the Cretaceous/Tertiary
boundary". PNAS. 95 (19): 11028–11029. Bibcode:1998PNAS...9511028P.
doi:10.1073/pnas.95.19.11028. PMC 33889 .
^ a b c Marshall CR, Ward PD (1996). "Sudden and Gradual Molluscan
Extinctions in the Latest
Cretaceous of Western European Tethys".
Science. 274 (5291): 1360–1363. Bibcode:1996Sci...274.1360M.
doi:10.1126/science.274.5291.1360. PMID 8910273.
^ Keller, Gerta (July 2001). "The end-cretaceous mass extinction in
the marine realm: year 2000 assessment". Planetary and Space Science.
49 (8): 817–830. Bibcode:2001P&SS...49..817K.
^ Bourgeois J (2009). "Chapter 3. GEOLOGIC EFFECTS AND RECORDS OF
TSUNAMIS". In Robinson, A.R.; Bernard, E.N. The Sea, Volume 15:
Tsunamis (Sea: Ideas and Observations on Progress in the Study of the
Seas) (pdf). Boston: Harvard University. ISBN 978-0-674-03173-9.
^ Lawton, T. F., K. W. Shipley, J. L. Aschoff, K. A. Giles and F.
J.Vega (2005). "Basinward transport of Chicxulub ejecta by
tsunami-induced backflow, La Popa basin, northeastern Mexico, and its
implications for distribution of impact-related deposits flanking the
Gulf of Mexico". Geology. 33 (2): 81–84.
Bibcode:2005Geo....33...81L. doi:10.1130/G21057.1. Retrieved
2012-03-29. CS1 maint: Multiple names: authors list (link)
^ Albertão, G. A.; P. P. Martins Jr. (1996). "A possible tsunami
deposit at the Cretaceous-
Tertiary boundary in Pernambuco,
northeastern Brazil". Sed. Geol. 104: 189–201.
^ Norris, R. D.; J. Firth; J. S. Blusztajn & G. Ravizza (2000).
"Mass failure of the North Atlantic margin triggered by the
Paleogene bolide impact". Geology. 28 (12): 1119–1122.
^ Bryant, Edward (June 2014). Tsunami: The Underrated Hazard.
Springer. p. 178. ISBN 9783319061337.
^ Signor III, PW; Lipps, JH (1982). "Sampling bias, gradual extinction
patterns, and catastrophes in the fossil record". In Silver LT;
Schultz PH. Geological implications of impacts of large asteroids and
comets on the Earth.
Special Publication 190. Boulder, Colorado:
Geological Society of America. pp. 291–296.
ISBN 0-8137-2190-3. OCLC 4434434112.
^ Mukhopadhyay, S.; et al. (2001). "A Short Duration of the
Tertiary Boundary Event: Evidence from Extraterrestrial
Helium-3". Science. 291: 1952–1955.
doi:10.1126/science.291.5510.1952. PMID 11239153.
^ De Laubenfels MW (1956). "
Dinosaur extinction: One more hypothesis".
Journal of Paleontology. 30 (1): 207–218. JSTOR 1300393.
^ Smit J., Klaver J. (1981). "Sanidine spherules at the
Tertiary boundary indicate a large impact event". Nature.
292 (5818): 47–49. Bibcode:1981Natur.292...47S.
doi:10.1038/292047a0. CS1 maint: Uses authors parameter (link)
^ Bohor B. F., Foord E. E., Modreski P. J., Triplehorn D. M. (1984).
"Mineralogic evidence for an impact event at the Cretaceous-Tertiary
boundary". Science. 224 (4651): 869. Bibcode:1984Sci...224..867B.
doi:10.1126/science.224.4651.867. PMID 17743194. CS1 maint:
Uses authors parameter (link)
^ Bohor B. F.; Modreski P. J.; Foord E. E. (1987). "Shocked Quartz in
Tertiary Boundary Clays: Evidence for a Global
Distribution". Science. 236 (4802): 705–709.
^ Bourgeois J., Hansen T. A., Wiberg P. A., Kauffman E. G. (1988). "A
tsunami deposit at the Cretaceous-
Tertiary boundary in Texas".
Science. 241 (4865): 567–570. Bibcode:1988Sci...241..567B.
doi:10.1126/science.241.4865.567. PMID 17774578. CS1 maint:
Uses authors parameter (link)
^ Pope KO, Ocampo AC, Kinsland GL, Smith R (1996). "Surface expression
of the Chicxulub crater". Geology. 24 (6): 527–530.
PMID 11539331. CS1 maint: Uses authors parameter (link)
^ David Perlman, "
Dinosaur extinction battle flares," accessed
^ Bottke WF, Vokrouhlický D, Nesvorný D (September 2007). "An
asteroid breakup 160 Myr ago as the probable source of the K/T
impactor". Nature. 449 (7158): 48–53. Bibcode:2007Natur.449...48B.
doi:10.1038/nature06070. PMID 17805288.
^ Majaess DJ, Higgins D, Molnar LA, Haegert MJ, Lane DJ, Turner DG,
Nielsen I (February 2009). "New Constraints on the
Baptistina, the Alleged Family Member of the K/T Impactor" (PDF). The
Journal of the Royal Astronomical Society of Canada. 103 (1): 7–10.
arXiv:0811.0171 . Bibcode:2009JRASC.103....7M. Archived from the
original (PDF) on 2010-11-29. CS1 maint: Uses authors parameter
^ Reddy V, Emery JP; Gaffey, MJ; Bottke, WF; Cramer A, Kelley MS
(December 2009). "Composition of 298 Baptistina: Implications for the
K/T impactor link". Meteoritics & Planetary Science. 44 (12):
^ "NASA's WISE Raises Doubt About
Asteroid Family Believed Responsible
Dinosaur Extinction". ScienceDaily. 20 September 2011. Retrieved
21 September 2011.
^ Robertson, D.S., Lewis, W.M., Sheehan, P.M. & Toon, O.B. (2013).
"K/Pg extinction: re-evaluation of the heat/fire hypothesis". Journal
of Geophysical Research: Biogeosciences. CS1 maint: Uses authors
^ Ohno, S.; et al. (2014). "Production of sulphate-rich vapour during
the Chicxulub impact and implications for ocean acidification". Nature
Geoscience. 7: 279–282. doi:10.1038/ngeo2095. Retrieved 22 January
^ Vellekoop, J.; et al. (2013). "Rapid short-term cooling following
the Chicxulub impact at the Cretaceous–
Proceedings of the National Academy of Sciences. 111: 7537–41.
doi:10.1073/pnas.1319253111. PMID 24821785.
^ Pope KO, Baines KH, Ocampo AC, Ivanov BA (1997). "Energy, volatile
production, and climatic effects of the Chicxulub Cretaceous/Tertiary
impact". Journal of Geophysical Research. 102 (E9): 21645–21664.
^ Morgan J, Lana C, Kersley A, Coles B, Belcher C, Montanari S,
Diaz-Martinez E, Barbosa A, Neumann V (2006). "Analyses of shocked
quartz at the global K-P boundary indicate an origin from a single,
high-angle, oblique impact at Chicxulub".
Earth and Planetary Science
Letters. 251 (3–4): 264–279. Bibcode:2006E&PSL.251..264M.
^ Brugger Julia, Feulner Georg, Petri Stefan (2016). "Baby, it's cold
outside: Climate model simulations of the effects of the asteroid
impact at the end of the Cretaceous". Geophysical Research Letters.
doi:10.1002/2016GL072241. CS1 maint: Multiple names: authors list
^ Kunio Kaiho & Naga Oshima (2017). Site of asteroid impact
changed the history of life on Earth: the low probability of mass
extinction. Scientific Reports 7, Article number: 14855.
^ Keller G, Adatte T, Gardin S, Bartolini A, Bajpai S; Adatte; Gardin;
Bartolini; Bajpai (2008). "Main Deccan volcanism phase ends near the
K–T boundary: Evidence from the Krishna-Godavari Basin, SE India".
Earth and Planetary Science Letters. 268 (3–4): 293–311.
doi:10.1016/j.epsl.2008.01.015. CS1 maint: Multiple names:
authors list (link)
^ Duncan RA, Pyle DG; Pyle (1988). "Rapid eruption of the Deccan flood
basalts at the Cretaceous/
Tertiary boundary". Nature. 333 (6176):
841–843. Bibcode:1988Natur.333..841D. doi:10.1038/333841a0.
^ Courtillot, Vincent (1990). "A volcanic eruption". Scientific
American. 263 (4): 85–92. doi:10.1038/scientificamerican1090-85.
^ Alvarez, W (1997). T. rex and the Crater of Doom. Princeton
University Press. pp. 130–146.
^ Renne, P. R.; et al. (2015). "State shift in Deccan volcanism at the
Paleogene boundary, possibly induced by impact". Science.
350 (6256): 76–78. Bibcode:2015Sci...350...76R.
doi:10.1126/science.aac7549. PMID 26430116.
^ Richards, M. A.; et al. (2015). "Triggering of the largest Deccan
eruptions by the Chicxulub impact". Geological Society of America
Bulletin. 127 (11–12): 1507–1520. Bibcode:2015GSAB..127.1507R.
^ Mullen L (October 13, 2004). "Debating the
Astrobiology Magazine. Retrieved 2012-03-29.
^ Mullen L (October 20, 2004). "Multiple impacts". Astrobiology
Magazine. Retrieved 2012-03-29.
^ Mullen L (November 3, 2004). "Shiva: Another K–T impact?".
Astrobiology Magazine. Retrieved 2012-03-29.
^ Chatterjee, Sankar (August 1997). "Multiple Impacts at the KT
Boundary and the Death of the Dinosaurs". 30th International
Geological Congress. 26. pp. 31–54.
^ Li, Liangquan; Keller, Gerta (1998). "Abrupt deep-sea warming at the
end of the Cretaceous". Geology. 26 (11): 995–998.
^ a b Petersen Sierra V., Dutton Andrea, Lohmann Kyger C. (2016).
Cretaceous extinction in Antarctica linked to both Deccan
volcanism and meteorite impact via climate change". Nature
Communications. 7: 12079. doi:10.1038/ncomms12079. CS1 maint:
Multiple names: authors list (link)
^ Alroy J (May 1998). "Cope's rule and the dynamics of body mass
evolution in North American fossil mammals". Science. 280 (5364):
doi:10.1126/science.280.5364.731. PMID 9563948.
^ Ericson PG; Anderson CL; Britton T; et al. (December 2006).
"Diversification of Neoaves: integration of molecular sequence data
and fossils". Biol. Lett. 2 (4): 543–7. doi:10.1098/rsbl.2006.0523.
PMC 1834003 . PMID 17148284.
^ Grimaldi, David A. (2007). Evolution of the Insects. Cambridge Univ
Pr (E). ISBN 0-511-12388-4.
Fortey, Richard (2005). Earth: An Intimate History. New York: Vintage
Books. ISBN 978-0-375-70620-2. OCLC 54537112.
Wikimedia Commons has media related to K/T Event.
"The Great Chicxulub Debate 2004". Geological Society of London. 2004.
Kring DA (2005). "Chicxulub Impact Event: Understanding the K–T
Boundary". NASA Space Imagery Center. Archived from the original on
June 29, 2007. Retrieved 2007-08-02.
Cowen R (2000). "The K–T extinction". University of California
Museum of Paleontology. Retrieved 2007-08-02.
"What killed the dinosaurs?". University of California Museum of
Paleontology. 1995. Retrieved 2007-08-02.
Papers and presentations resulting from the 2016 Chicxulub drilling
Paleogene extinction event
K–Pg boundary craters
Carboniferous rainforest collapse
Millions of years before present
Dinosauromorpha and relatives)
Major clades underlined
See also categories:
Paleogene extinction event
Background extinction rate
Extinct in the wild
Theories & concepts
Extinction risk from global warming
Field of Bullets
Latent extinction risk
Major extinction events
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Jurassic or Tithonian
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International Union for Conservation of Nature
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Decline in amphibian populations
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