Cretaceous-Tertiary

In both the Rocky Mountain and the Mississippi Embayment regions it is often difficult to distinguish Upper Cretaceous from lower Tertiary rocks on the basis of physical characteristics; the transition can be recognized with relative ease, however, on the basis of abrupt qualitative changes in plant microfossils. Many Cretaceous species vanish and new species appear in the Paleocene. In both regions the Paleocene yields fewer species than does the underlying Cretaceous. A pronounced difference exists between the Late Cretaceous pollen and spore floras of the two regions. The spore-pollen assemblage from the Rocky Mountains is partially characterized by the presence of Aquilapollenites, Proteacidites, Wodehouseia,and an unnamed species of Tricolpites.These taxa are not found in the Late Cretaceous of the Mississippi Embayment region. The embayment region yields Rugubivesiculites,an unnamed species of Araucariacites,and several genera belonging to the Normapolles group that are not found in the Rocky Mountain region. The Mississippi Embayment Cretaceous and Paleocene pollen floras show greater similarities to pollen floras from Europe than to those from the northern Rocky Mountains. The Rocky Mountain pollen floras exhibit closer similarities to the Alaskan and Siberian floras. It is suggested that the floral dissimilarity between the Mississippi Embayment and the northern Rocky Mountain regions may be accounted for by the separation of the Rocky Mountain province from the Mississippi Embayment province during Late Cretaceous time by the great north-trending Cretaceous epeiric sea. It is further suggested that the floral changes across the Cretaceous-Tertiary transition may have been caused by slight climatic changes brought about by uplift or by withdrawal of the tempering influence of the epeiric sea.

@incollection{doi101130spe127p65,
    author = "Tschudy, Robert H.",
    title = "Palynology of the Cretaceous-Tertiary Boundary in the Northern Rocky Mountain and Mississippi Embayment Regions",
    year = "1970",
    booktitle = "Geological Society of America eBooks",
    abstract = "In both the Rocky Mountain and the Mississippi Embayment regions it is often difficult to distinguish Upper Cretaceous from lower Tertiary rocks on the basis of physical characteristics; the transition can be recognized with relative ease, however, on the basis of abrupt qualitative changes in plant microfossils. Many Cretaceous species vanish and new species appear in the Paleocene. In both regions the Paleocene yields fewer species than does the underlying Cretaceous. A pronounced difference exists between the Late Cretaceous pollen and spore floras of the two regions. The spore-pollen assemblage from the Rocky Mountains is partially characterized by the presence of Aquilapollenites, Proteacidites, Wodehouseia,and an unnamed species of Tricolpites.These taxa are not found in the Late Cretaceous of the Mississippi Embayment region. The embayment region yields Rugubivesiculites,an unnamed species of Araucariacites,and several genera belonging to the Normapolles group that are not found in the Rocky Mountain region. The Mississippi Embayment Cretaceous and Paleocene pollen floras show greater similarities to pollen floras from Europe than to those from the northern Rocky Mountains. The Rocky Mountain pollen floras exhibit closer similarities to the Alaskan and Siberian floras. It is suggested that the floral dissimilarity between the Mississippi Embayment and the northern Rocky Mountain regions may be accounted for by the separation of the Rocky Mountain province from the Mississippi Embayment province during Late Cretaceous time by the great north-trending Cretaceous epeiric sea. It is further suggested that the floral changes across the Cretaceous-Tertiary transition may have been caused by slight climatic changes brought about by uplift or by withdrawal of the tempering influence of the epeiric sea.",
    url = "https://doi.org/10.1130/spe127-p65",
    doi = "10.1130/spe127-p65",
    openalex = "W2346678123"
}

@article{russell1971the14,
    author = "Russell, D. A",
    title = "The disappearance of the dinosaurs",
    year = "1971",
    journal = "Canadian Geographic Journal, v. 83, p. 204-215",
    note = "talkorigins\_source = {true}; raw\_reference = {Russell, D. A., 1971, The disappearance of the dinosaurs: Canadian Geographic Journal, v. 83, p. 204-215.}"
}

Platinum metals are depleted in the earth's crust relative to their cosmic abundance; concentrations of these elements in deep-sea sediments may thus indicate influxes of extraterrestrial material. Deep-sea limestones exposed in Italy, Denmark, and New Zealand show iridium increases of about 30, 160, and 20 times, respectively, above the background level at precisely the time of the Cretaceous-Tertiary extinctions, 65 million years ago. Reasons are given to indicate that this iridium is of extraterrestrial origin, but did not come from a nearby supernova. A hypothesis is suggested which accounts for the extinctions and the iridium observations. Impact of a large earth-crossing asteroid would inject about 60 times the object's mass into the atmosphere as pulverized rock; a fraction of this dust would stay in the stratosphere for several years and be distributed worldwide. The resulting darkness would suppress photosynthesis, and the expected biological consequences match quite closely the extinctions observed in the paleontological record. One prediction of this hypothesis has been verified: the chemical composition of the boundary clay, which is thought to come from the stratospheric dust, is markedly different from that of clay mixed with the Cretaceous and Tertiary limestones, which are chemically similar to each other. Four different independent estimates of the diameter of the asteroid give values that lie in the range 10 ± 4 kilometers.

@article{alvarez1980extraterrestrial,
    author = "Alvarez, Luis W. and Alvarez, Walter and Asaro, Frank and Michel, Helen V.",
    title = "Extraterrestrial Cause for the Cretaceous-Tertiary Extinction",
    year = "1980",
    journal = "Science",
    abstract = "Platinum metals are depleted in the earth's crust relative to their cosmic abundance; concentrations of these elements in deep-sea sediments may thus indicate influxes of extraterrestrial material. Deep-sea limestones exposed in Italy, Denmark, and New Zealand show iridium increases of about 30, 160, and 20 times, respectively, above the background level at precisely the time of the Cretaceous-Tertiary extinctions, 65 million years ago. Reasons are given to indicate that this iridium is of extraterrestrial origin, but did not come from a nearby supernova. A hypothesis is suggested which accounts for the extinctions and the iridium observations. Impact of a large earth-crossing asteroid would inject about 60 times the object's mass into the atmosphere as pulverized rock; a fraction of this dust would stay in the stratosphere for several years and be distributed worldwide. The resulting darkness would suppress photosynthesis, and the expected biological consequences match quite closely the extinctions observed in the paleontological record. One prediction of this hypothesis has been verified: the chemical composition of the boundary clay, which is thought to come from the stratospheric dust, is markedly different from that of clay mixed with the Cretaceous and Tertiary limestones, which are chemically similar to each other. Four different independent estimates of the diameter of the asteroid give values that lie in the range 10 ± 4 kilometers.",
    url = "https://doi.org/10.1126/science.208.4448.1095",
    doi = "10.1126/science.208.4448.1095",
    number = "4448",
    openalex = "W2110619496",
    pages = "1095-1108",
    volume = "208",
    references = "doi101007bf00212446, doi1010160016703773900665, doi1010160031018268900473, doi101038242032a0, doi101038267403a0, doi1010970001069419540800000019, doi101126science18441411079, doi10113000167606197788367ucmsag20co2, doi10113000167606197788374ucmsag20co2, doi10113000167606197788383ucmsag20co2, doi101146annurevea07050179001115, hays1971faunal"
}

@misc{alvarez1980extraterrestrial1,
    author = "Alvarez, L. W. and Alveraz, W. and Asaro, F. and Michel, H",
    title = "Extraterrestrial cause for the Creataceous-Tertiary extinction",
    year = "1980",
    howpublished = "Science, v. 208, p. 1095- 1108",
    note = "talkorigins\_source = {true}; raw\_reference = {Alvarez, L. W., Alveraz, W., Asaro, F., and Michel, H., 1980, Extraterrestrial cause for the Creataceous-Tertiary extinction: Science, v. 208, p. 1095- 1108.}"
}

@article{alveraz1980extraterrestrial3,
    author = "Alveraz, L. W. and Alveraz, W. and Asaro, F. and Michel, H. V",
    title = "Extraterrestrial cause for the Cretaceous-Tertiary extinction",
    year = "1980",
    journal = "Science, v. 208, p. 1095-1108; See also Letters and authors' reply, Science , vol. 211, pp. 648-656",
    note = "talkorigins\_source = {true}; raw\_reference = {Alveraz, L. W., Alveraz, W., Asaro, F., and Michel, H. V., 1980, Extraterrestrial cause for the Cretaceous-Tertiary extinction: Science, v. 208, p. 1095-1108; See also Letters and authors' reply, Science , vol. 211, pp. 648-656.}"
}

@article{doi101038285198a0,
    author = "Smit, Jan and Hertogen, J.",
    title = "An extraterrestrial event at the Cretaceous–Tertiary boundary",
    year = "1980",
    journal = "Nature",
    url = "https://doi.org/10.1038/285198a0",
    doi = "10.1038/285198a0",
    openalex = "W1982572431",
    references = "doi1010160031018268900473, doi10113000167606197788367ucmsag20co2, doi101146annurevea07050179001115"
}

@misc{emiliani1980death6,
    author = "Emiliani, C",
    title = "Death and renovation at the end of the Mesozoic",
    year = "1980",
    howpublished = "Eos, v. 61, no. 1, p. 505-506",
    note = "talkorigins\_source = {true}; raw\_reference = {Emiliani, C., 1980, Death and renovation at the end of the Mesozoic: Eos, v. 61, no. 1, p. 505-506.}"
}

@incollection{alvarez1981extraterrestrial,
    author = "Alvarez, L.W. and Alvarez, W. and Asaro, F. and Michel, H.V.",
    title = "EXTRATERRESTRIAL CAUSE FOR THE CRETACEOUS-TERTIARY EXTINCTION: EXPERIMENT AND THEORY",
    year = "1981",
    booktitle = "Applications of Space Developments",
    url = "https://doi.org/10.1016/b978-0-08-026729-6.50022-8",
    doi = "10.1016/b978-0-08-026729-6.50022-8",
    openalex = "W174742430",
    pages = "241-271",
    references = "alvarez1981extraterrestrial, doi101007bf00212446, doi1010160031018268900473, doi101038242032a0, doi101038267403a0, doi101111j147547541969tb00627x, doi101126science18441411079, doi10113000167606197788374ucmsag20co2, doi10113000167606197788383ucmsag20co2, doi101146annurevea07050179001115, doi102110pec77250019"
}

An iridium abundance anomaly, with concentrations up to 5000 parts per trillion over a background level of 4 to 20 parts per trillion, has been located in sedimentary rocks laid down under freshwater swamp conditions in the Raton Basin of northeastern New Mexico. The anomaly occurs at the base of a coal bed, at the same stratigraphic position at which several well-known species of Cretaceous-age pollen became extinct.

@article{doi101126science21445271341,
    author = "Orth, C. J. and Gilmore, J. S. and Knight, J.D. and Pillmore, Charles L. and Tschudy, Robert H. and Fassett, James E.",
    title = "An Iridium Abundance Anomaly at the Palynological Cretaceous-Tertiary Boundary in Northern New Mexico",
    year = "1981",
    journal = "Science",
    abstract = "An iridium abundance anomaly, with concentrations up to 5000 parts per trillion over a background level of 4 to 20 parts per trillion, has been located in sedimentary rocks laid down under freshwater swamp conditions in the Raton Basin of northeastern New Mexico. The anomaly occurs at the base of a coal bed, at the same stratigraphic position at which several well-known species of Cretaceous-age pollen became extinct.",
    url = "https://doi.org/10.1126/science.214.4527.1341",
    doi = "10.1126/science.214.4527.1341",
    openalex = "W1980328862",
    references = "alvarez1980extraterrestrial, doi101038285198a0, doi101126science2094459921, doi1021724365567, doi103133gq823"
}

Iridium is depleted in the earth’s crust relative to its normal solar system abundance. Several hundred measurements by at least seven laboratories have disclosed an iridium abundance anomaly at the Cretaceous/Tertiary (C/T) boundary in 36 sites worldwide. Discovery of the first iridium anomaly in nonmarine sediments, by Charles Orth and his colleagues, shows that the iridium was not extracted from sea water. Sediment starvation and a nearby supernova have also been eliminated as possible sources. Impact of a large extraterrestrial object is now widely accepted as the best explanation of the iridium anomaly. Paleomagnetic reversal stratigraphy of four marine and five non-marine C/T boundary sections is consistent with simultaneous extinction worldwide, but does not prove it. Ultra-high-resolution stratigraphic studies at Caravaca, in southern Spain, by Jan Smit, gave an unparalleled record of the extinction of the planktonic foraminifera and the associated geochemical patterns. Au/Ir and Pt/Ir ratios from two C/T boundary clays indicate a type I carbonaceous chondrite composition for the impacting object. Iridium anomalies are known from two other stratigraphic horizons, in each case associated with direct evidence for an extraterrestrial impact: in the Pliocene, with chondritic ablation debris, and in the late Eocene with microtektites. The C/T impact site has not been located. Two interesting candidate sites are the circular sea-floor features west of Portugal and the Deccan Traps of India. There is a 20% probability that impact occurred on sea floor that has subsequently been subducted. Recent computer modeling of impact processes is yielding important information. The killing mechanism has not yet been established, but both temperature changes and darkness due to atmospheric dust are probable contributors. Darkness would have lasted a few months, rather than our originally suggested few years; this is indicated by (1) calculated rapid dispersal of dust in ballistic trajectories, (2) more rapid settling of heavier, coagulated dust particles, (3) calculated effects of darkness on phytoplankton, and (4) compatibility of the plant record with a few months—but not with a few years—of darkness.

@incollection{doi101130spe190p305,
    author = "Álvarez, Walter and Alvarez, Luis W. and Asaro, Frank and Michel, Helen V.",
    title = "Current status of the impact theory for the terminal Cretaceous extinction",
    year = "1982",
    booktitle = "Geological Society of America eBooks",
    abstract = "Iridium is depleted in the earth’s crust relative to its normal solar system abundance. Several hundred measurements by at least seven laboratories have disclosed an iridium abundance anomaly at the Cretaceous/Tertiary (C/T) boundary in 36 sites worldwide. Discovery of the first iridium anomaly in nonmarine sediments, by Charles Orth and his colleagues, shows that the iridium was not extracted from sea water. Sediment starvation and a nearby supernova have also been eliminated as possible sources. Impact of a large extraterrestrial object is now widely accepted as the best explanation of the iridium anomaly. Paleomagnetic reversal stratigraphy of four marine and five non-marine C/T boundary sections is consistent with simultaneous extinction worldwide, but does not prove it. Ultra-high-resolution stratigraphic studies at Caravaca, in southern Spain, by Jan Smit, gave an unparalleled record of the extinction of the planktonic foraminifera and the associated geochemical patterns. Au/Ir and Pt/Ir ratios from two C/T boundary clays indicate a type I carbonaceous chondrite composition for the impacting object. Iridium anomalies are known from two other stratigraphic horizons, in each case associated with direct evidence for an extraterrestrial impact: in the Pliocene, with chondritic ablation debris, and in the late Eocene with microtektites. The C/T impact site has not been located. Two interesting candidate sites are the circular sea-floor features west of Portugal and the Deccan Traps of India. There is a 20\% probability that impact occurred on sea floor that has subsequently been subducted. Recent computer modeling of impact processes is yielding important information. The killing mechanism has not yet been established, but both temperature changes and darkness due to atmospheric dust are probable contributors. Darkness would have lasted a few months, rather than our originally suggested few years; this is indicated by (1) calculated rapid dispersal of dust in ballistic trajectories, (2) more rapid settling of heavier, coagulated dust particles, (3) calculated effects of darkness on phytoplankton, and (4) compatibility of the plant record with a few months—but not with a few years—of darkness.",
    url = "https://doi.org/10.1130/spe190-p305",
    doi = "10.1130/spe190-p305",
    openalex = "W1950866488"
}

The mass-extinction event at the Cretaceous/Tertiary boundary (C/T in text; K-T on figures) exterminated all but one species of the planktonic Foraminifera (Guembelitria cretaceaCushman). Although not all details have been clarified yet, all Paleocene planktonic Foraminifera may have evolved from this sole survivor. Globigerina minutulaLuterbacher and Premoli Silva is the first true Paleocene species to appear; it develops into Globigerina fringaSubbotina, and later on probably into Globigerina eugubinaLuterbacher and Premoli Silva. Essentially, the stratigraphy of several complete sections shows a similar pattern: abrupt extinction of plankton followed by deposition of a thin lamina with high concentrations of siderophile elements, considered as the direct fallout level of the impact event. This lamina is followed by a 1- to 30-cm-thick clay or marl layer (which represents the normal background supply of hemipelagic clay) and a gradual return to calcareous sedimentation associated with the appearance of the first new Paleocene species. The biostratigraphy of the Gredero section in southeast Spain is analyzed in detail, complemented with data from the Kef section in Northern Tunisia. A new zone, the Guembelitria cretaceaZone, which contains only G. cretacea,and possibly Globotruncanella monmouthensis(Olsson) and Globigerinelloides messinaeBrönnimann in situ, is established at the base of the Tertiary. It is essentially the same as the C/T boundary clay. New taxonomic descriptions are given of G. cretacea, Globigerina minutula, G. fringa, G. eugubina,and Globotruncanella caravacaensisn. sp. Preliminary results of a paleomagnetic survey are used to calculate sediment accumulation rates, from which the mass extinction is inferred to have occurred within 50 years and a new stable planktonic fauna re-established within 35,000 years. The earliest Paleocene faunas are highly unstable. Different species successively become dominant and show a rapid evolutionary development. The initial development thus is both explosive and unstable and seems to be consistent with the punctuated mode of evolution.

@incollection{doi101130spe190p329,
    author = "Smit, Jan",
    title = "Extinction and evolution of planktonic foraminifera after a major impact at the Cretaceous/Tertiary boundary",
    year = "1982",
    booktitle = "Geological Society of America eBooks",
    abstract = "The mass-extinction event at the Cretaceous/Tertiary boundary (C/T in text; K-T on figures) exterminated all but one species of the planktonic Foraminifera (Guembelitria cretaceaCushman). Although not all details have been clarified yet, all Paleocene planktonic Foraminifera may have evolved from this sole survivor. Globigerina minutulaLuterbacher and Premoli Silva is the first true Paleocene species to appear; it develops into Globigerina fringaSubbotina, and later on probably into Globigerina eugubinaLuterbacher and Premoli Silva. Essentially, the stratigraphy of several complete sections shows a similar pattern: abrupt extinction of plankton followed by deposition of a thin lamina with high concentrations of siderophile elements, considered as the direct fallout level of the impact event. This lamina is followed by a 1- to 30-cm-thick clay or marl layer (which represents the normal background supply of hemipelagic clay) and a gradual return to calcareous sedimentation associated with the appearance of the first new Paleocene species. The biostratigraphy of the Gredero section in southeast Spain is analyzed in detail, complemented with data from the Kef section in Northern Tunisia. A new zone, the Guembelitria cretaceaZone, which contains only G. cretacea,and possibly Globotruncanella monmouthensis(Olsson) and Globigerinelloides messinaeBrönnimann in situ, is established at the base of the Tertiary. It is essentially the same as the C/T boundary clay. New taxonomic descriptions are given of G. cretacea, Globigerina minutula, G. fringa, G. eugubina,and Globotruncanella caravacaensisn. sp. Preliminary results of a paleomagnetic survey are used to calculate sediment accumulation rates, from which the mass extinction is inferred to have occurred within 50 years and a new stable planktonic fauna re-established within 35,000 years. The earliest Paleocene faunas are highly unstable. Different species successively become dominant and show a rapid evolutionary development. The initial development thus is both explosive and unstable and seems to be consistent with the punctuated mode of evolution.",
    url = "https://doi.org/10.1130/spe190-p329",
    doi = "10.1130/spe190-p329",
    openalex = "W2418914985"
}

During the past year we have been measuring trace element abundances and searching for anomalously high iridium (Ir) concentrations in continental sedimentary rocks that span the Cretaceous-Tertiary boundary in the Raton and San Juan Basins of northern New Mexico and southern Colorado. Using neutron activation and radiochemical separations, we have identified anomalous concentrations of Ir in samples from two sites in the Raton Basin: in a drill core at York Canyon, about 50 km west of Raton, New Mexico, and in a road cut near the city of Raton. In both cases the anomaly occurs essentially at the base of thin coal beds, across a thickness span of only a few cm and at the same level at which several species of Cretaceous pollen become extinct and the ratio of angiosperm pollen to fern spores drops sharply. The Ir surface density ranges from 8 to 40 × 10 −9g cm −2. In the York Canyon core the Ir concentration reaches a value of 5.6 × 10 −9g/g of rock over a local background of about 10 −11g/g; the Pt abundance distribution is similar to that for Ir, while Au reaches its maximum concentration about 10 cm below the Ir peak. Se, V, Cr, Mn, Co, and Zn are about two-fold more abundant at the anomaly zone than in adjacent zones, and mass spectrometric 244Pu analysis showed the 244Pu/Ir atom ratio ⩽ 1 × 10 7. In the San Juan Basin we have located a small Ir spike (55 × 10 −12g/g over a local background of 8 × 10 −12g/g) that is accompanied by high concentrations of Co and Mn. It is thought to be due to geochemical enrichment processes.

@incollection{doi101130spe190p423,
    author = "Orth, C. J. and Gilmore, J. S. and Knight, J.D. and Pillmore, Charles L. and Tschudy, Robert H. and Fassett, James E.",
    title = "Iridium abundance measurements across the Cretaceous/Tertiary boundary in the San Juan and Raton Basins of northern New Mexico",
    year = "1982",
    booktitle = "Geological Society of America eBooks",
    abstract = "During the past year we have been measuring trace element abundances and searching for anomalously high iridium (Ir) concentrations in continental sedimentary rocks that span the Cretaceous-Tertiary boundary in the Raton and San Juan Basins of northern New Mexico and southern Colorado. Using neutron activation and radiochemical separations, we have identified anomalous concentrations of Ir in samples from two sites in the Raton Basin: in a drill core at York Canyon, about 50 km west of Raton, New Mexico, and in a road cut near the city of Raton. In both cases the anomaly occurs essentially at the base of thin coal beds, across a thickness span of only a few cm and at the same level at which several species of Cretaceous pollen become extinct and the ratio of angiosperm pollen to fern spores drops sharply. The Ir surface density ranges from 8 to 40 × 10 −9g cm −2. In the York Canyon core the Ir concentration reaches a value of 5.6 × 10 −9g/g of rock over a local background of about 10 −11g/g; the Pt abundance distribution is similar to that for Ir, while Au reaches its maximum concentration about 10 cm below the Ir peak. Se, V, Cr, Mn, Co, and Zn are about two-fold more abundant at the anomaly zone than in adjacent zones, and mass spectrometric 244Pu analysis showed the 244Pu/Ir atom ratio ⩽ 1 × 10 7. In the San Juan Basin we have located a small Ir spike (55 × 10 −12g/g over a local background of 8 × 10 −12g/g) that is accompanied by high concentrations of Co and Mn. It is thought to be due to geochemical enrichment processes.",
    url = "https://doi.org/10.1130/spe190-p423",
    doi = "10.1130/spe190-p423",
    openalex = "W1847538392"
}

@misc{thierstein1982terminal16,
    author = "Thierstein, H. R",
    title = "Terminal Cretaceous Plankton Extinctions, in Silver, L. T., and Schultz, P. H., eds., Geological Implications of Impacts of Large Asteroids and Comets on the Earth",
    year = "1982",
    howpublished = "Boulder, Colorado, Geological Society of America, p. 385-399; Geological Society of America Special Paper No. 190",
    note = "talkorigins\_source = {true}; raw\_reference = {Thierstein, H. R., 1982, Terminal Cretaceous Plankton Extinctions, in Silver, L. T., and Schultz, P. H., eds., Geological Implications of Impacts of Large Asteroids and Comets on the Earth: Boulder, Colorado, Geological Society of America, p. 385-399; Geological Society of America Special Paper No. 190.}"
}

@misc{axelrod1984an4,
    author = "Axelrod, D. I",
    title = "An interpretation of Cretaceous and Tertiary biota in polar regions",
    year = "1984",
    howpublished = "Palaeogeography, Palaeoclimatology, Palaeoecology, v. 45, p. 105-147",
    note = "talkorigins\_source = {true}; raw\_reference = {Axelrod, D. I., 1984, An interpretation of Cretaceous and Tertiary biota in polar regions: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 45, p. 105-147.}"
}

Iridium concentrations are anomalously high at the palynological Cretaceous-Tertiary boundary in fluvial sedimentary rocks of the lower part of the Raton Formation at several localities in the Raton Basin of New Mexico and Colorado. The iridium anomaly is associated with a thin bed of kaolinitic claystone in a discontinuous carbonaceous shale and coal sequence.

@article{doi101126science22346411180,
    author = "Pillmore, Charles L. and Tschudy, Robert H. and Orth, C. J. and Gilmore, J. S. and Knight, J.D.",
    title = "Geologic Framework of Nonmarine Cretaceous-Tertiary Boundary Sites, Raton Basin, New Mexico and Colorado",
    year = "1984",
    journal = "Science",
    abstract = "Iridium concentrations are anomalously high at the palynological Cretaceous-Tertiary boundary in fluvial sedimentary rocks of the lower part of the Raton Formation at several localities in the Raton Basin of New Mexico and Colorado. The iridium anomaly is associated with a thin bed of kaolinitic claystone in a discontinuous carbonaceous shale and coal sequence.",
    url = "https://doi.org/10.1126/science.223.4641.1180",
    doi = "10.1126/science.223.4641.1180",
    openalex = "W2033629863"
}

A thin claystone layer found in nonmarine rocks at the palynological Cretaceous-Tertiary boundary in eastern Montana contains an anomalously high value of iridium. The nonclay fraction is mostly quartz with minor feldspar, and some of these grains display planar features. These planar features are related to specific crystallographic directions in the quartz lattice. The shocked quartz grains also exhibit asterism and have lowered refractive indices. All these mineralogical features are characteristic of shock metamorphism and are compelling evidence that the shocked grains are the product of a high velocity impact between a large extraterrestrial body and the earth. The shocked minerals represent silicic target material injected into the stratosphere by the impact of the projectile.

@article{doi101126science2244651867,
    author = "Bohor, B. F. and Foord, Eugene E. and Modreski, Peter J. and Triplehorn, Don M.",
    title = "Mineralogic Evidence for an Impact Event at the Cretaceous-Tertiary Boundary",
    year = "1984",
    journal = "Science",
    abstract = "A thin claystone layer found in nonmarine rocks at the palynological Cretaceous-Tertiary boundary in eastern Montana contains an anomalously high value of iridium. The nonclay fraction is mostly quartz with minor feldspar, and some of these grains display planar features. These planar features are related to specific crystallographic directions in the quartz lattice. The shocked quartz grains also exhibit asterism and have lowered refractive indices. All these mineralogical features are characteristic of shock metamorphism and are compelling evidence that the shocked grains are the product of a high velocity impact between a large extraterrestrial body and the earth. The shocked minerals represent silicic target material injected into the stratosphere by the impact of the projectile.",
    url = "https://doi.org/10.1126/science.224.4651.867",
    doi = "10.1126/science.224.4651.867",
    openalex = "W2038487387",
    references = "alvarez1980extraterrestrial, doi101007bf00377477, doi101016001910356990061x, doi101126science21445271341, doi101130spe127p65, doi101130spe190p305, doi101130spe190p423, doi102475ajs2639786"
}

The palynologically defined Cretaceous-Tertiary boundary in the western interior of North America occurs at the top of an iridium-rich clay layer. The boundary is characterized by the abrupt disappearance of certain pollen species, immediately followed by a pronounced, geologically brief change in the ratio of fern spores to angiosperm pollen. The occurrence of these changes at two widely separated sites implies continentwide disruption of the terrestrial ecosystem, probably caused by a major catastrophic event at the end of the period.

@article{doi101126science22546661030,
    author = "Tschudy, Robert H. and Pillmore, Charles L. and Orth, C. J. and Gilmore, J. S. and Knight, J.D.",
    title = "Disruption of the Terrestrial Plant Ecosystem at the Cretaceous-Tertiary Boundary, Western Interior",
    year = "1984",
    journal = "Science",
    abstract = "The palynologically defined Cretaceous-Tertiary boundary in the western interior of North America occurs at the top of an iridium-rich clay layer. The boundary is characterized by the abrupt disappearance of certain pollen species, immediately followed by a pronounced, geologically brief change in the ratio of fern spores to angiosperm pollen. The occurrence of these changes at two widely separated sites implies continentwide disruption of the terrestrial ecosystem, probably caused by a major catastrophic event at the end of the period.",
    url = "https://doi.org/10.1126/science.225.4666.1030",
    doi = "10.1126/science.225.4666.1030",
    openalex = "W2045965176",
    references = "alvarez1980extraterrestrial, doi101038307224a0, doi101086628630, doi101126science21445271341, doi101126science22346411180, doi101126science2244651867, doi101130spe190p305, doi1023072399088, openalexw2334406281"
}

@techreport{leipzig1984stratigraphy8,
    author = "Leipzig, M. R",
    title = "Stratigraphy, Sedimentology and Depositional Environments of the Late Cretaceous/Early Tertiary Transition, Eastern San Juan Basin, New Mexico",
    year = "1984",
    howpublished = "New Mexico Bureau of Mines and Mineral Resources Bulletin, v. 142, no. 5, p. 109-256",
    note = "talkorigins\_source = {true}; raw\_reference = {Leipzig, M. R., 1984, Stratigraphy, Sedimentology and Depositional Environments of the Late Cretaceous/Early Tertiary Transition, Eastern San Juan Basin, New Mexico: New Mexico Bureau of Mines and Mineral Resources Bulletin, v. 142, no. 5, p. 109-256.}"
}

@article{mccartney1984the9,
    author = "McCartney, K",
    title = "The Cretaceous-Tertiary extinctions",
    year = "1984",
    journal = "Journal of Geological Education, v. 32, p. 306-309",
    note = "talkorigins\_source = {true}; raw\_reference = {McCartney, K., 1984, The Cretaceous-Tertiary extinctions: Journal of Geological Education, v. 32, p. 306-309.}"
}

@misc{officer1984terminal10,
    author = "Officer, C. B. and Drake, C. L",
    title = "Terminal Cretaceous events",
    year = "1984",
    howpublished = "Science, v. 227, p. 1161-1167",
    note = "talkorigins\_source = {true}; raw\_reference = {Officer, C. B., and Drake, C. L., 1984, Terminal Cretaceous events: Science, v. 227, p. 1161-1167.}"
}

@misc{russell1984the15,
    author = "Russell, D. A",
    title = "The gradual decline of the dinosaurs - fact or fallacy?",
    year = "1984",
    howpublished = "Nature, v. 307, p. 360-361",
    note = "talkorigins\_source = {true}; raw\_reference = {Russell, D. A., 1984, The gradual decline of the dinosaurs - fact or fallacy?: Nature, v. 307, p. 360-361.}"
}

Clay samples from three Cretaceous-Tertiary boundary sites contain 0.36 to 0.58 percent graphitic carbon, mainly as fluffy aggregates of 0.1 to 0.5 micrometers-apparently a worldwide layer of soot. It may have been produced by wildfires triggered by a giant meteorite. This carbon, corresponding to a global abundance of 0.021 +/- 0.006 gram per square centimeter, could have greatly enhanced the darkening and cooling of the earth by rock dust, which has been suggested as a cause of the extinctions. The surprisingly large amount of soot (10 percent of the present biomass of the earth) implies either that much of the earth's vegetation burned down or that substantial amounts of fossil fuels were ignited also. The particle-size distribution of the soot is similar to that assumed for the smoke cloud of "nuclear winter," but the global distribution is more uniform and the amounts are much greater, suggesting that soot production by large wildfires is about 10 times more efficient that has been assumed for a nuclear winter. Thus cooling would be more pervasive and lasting. No trace of meteoritic noble gases and no meteoritic spinel were found in these carbon fractions. Accordingly, limits can be set on the mass fraction of the meteorite that escaped degassing (</=3 x 10(-5)) or vaporization (</=0.04). Thus it seems unlikely that comets contributed significant amounts of prebiotic organic matter to the primitive earth.

@article{doi101126science2304722167,
    author = "Wolbach, Wendy S. and Lewis, R. S. and Anders, Edward",
    title = "Cretaceous Extinctions: Evidence for Wildfires and Search for Meteoritic Material",
    year = "1985",
    journal = "Science",
    abstract = {Clay samples from three Cretaceous-Tertiary boundary sites contain 0.36 to 0.58 percent graphitic carbon, mainly as fluffy aggregates of 0.1 to 0.5 micrometers-apparently a worldwide layer of soot. It may have been produced by wildfires triggered by a giant meteorite. This carbon, corresponding to a global abundance of 0.021 +/- 0.006 gram per square centimeter, could have greatly enhanced the darkening and cooling of the earth by rock dust, which has been suggested as a cause of the extinctions. The surprisingly large amount of soot (10 percent of the present biomass of the earth) implies either that much of the earth's vegetation burned down or that substantial amounts of fossil fuels were ignited also. The particle-size distribution of the soot is similar to that assumed for the smoke cloud of "nuclear winter," but the global distribution is more uniform and the amounts are much greater, suggesting that soot production by large wildfires is about 10 times more efficient that has been assumed for a nuclear winter. Thus cooling would be more pervasive and lasting. No trace of meteoritic noble gases and no meteoritic spinel were found in these carbon fractions. Accordingly, limits can be set on the mass fraction of the meteorite that escaped degassing (</=3 x 10(-5)) or vaporization (</=0.04). Thus it seems unlikely that comets contributed significant amounts of prebiotic organic matter to the primitive earth.},
    url = "https://doi.org/10.1126/science.230.4722.167",
    doi = "10.1126/science.230.4722.167",
    openalex = "W2067579175",
    references = "doi101073pnas802627, doi101126science22346411183, doi101126science22546661030"
}

ABSTRACT The presence of nodosaurid ankylosaurs in the Lance, Hell Creek, and Laramie formations of western North America is confirmed, thereby extending the geochronological range of this family into the Maastrichtian (Lancian). The material includes a cervical spine and a skull referable to Edmontonia sp., and numerous teeth, plates and a basioccipital, which are questionably assigned to Edmontonia sp. Comparison of the amount of nodosaurid material known from the Judith River Formation (Campanian) with that from the Lancian deposits indicates a substantial decrease in the relative abundance of nodosaurids in the Maastrichtian. Furthermore, the stratigraphic distribution of these nodosaurs is apparently limited to the lower part of the Lancian deposits, suggesting that they became extinct before the end of the Cretaceous. If true, this would support the hypothesis that the dinosaur extinction at the end of the Maastrichtian was gradual, not catastrophic.

@article{doi10108002724634198610011619,
    author = "Carpenter, Kenneth and Breithaupt, Brent H.",
    title = "Latest Cretaceous occurrence of nodosaurid ankylosaurs (Dinosauria, Ornithischia) in Western North America and the gradual extinction of the dinosaurs",
    year = "1986",
    journal = "Journal of Vertebrate Paleontology",
    abstract = "ABSTRACT The presence of nodosaurid ankylosaurs in the Lance, Hell Creek, and Laramie formations of western North America is confirmed, thereby extending the geochronological range of this family into the Maastrichtian (Lancian). The material includes a cervical spine and a skull referable to Edmontonia sp., and numerous teeth, plates and a basioccipital, which are questionably assigned to Edmontonia sp. Comparison of the amount of nodosaurid material known from the Judith River Formation (Campanian) with that from the Lancian deposits indicates a substantial decrease in the relative abundance of nodosaurids in the Maastrichtian. Furthermore, the stratigraphic distribution of these nodosaurs is apparently limited to the lower part of the Lancian deposits, suggesting that they became extinct before the end of the Cretaceous. If true, this would support the hypothesis that the dinosaur extinction at the end of the Maastrichtian was gradual, not catastrophic.",
    url = "https://doi.org/10.1080/02724634.1986.10011619",
    doi = "10.1080/02724634.1986.10011619",
    openalex = "W1983683915",
    references = "doi101017s0094837300008071, doi101127njgpm19831983141"
}

@misc{retallack1986cretaceoustertiary13,
    author = "Retallack, G. and Leahy, G. D",
    title = "Cretaceous-Tertiary dinosaur extinction",
    year = "1986",
    howpublished = "Science, v. 234, p. 1170-1171",
    note = "talkorigins\_source = {true}; raw\_reference = {Retallack, G., and Leahy, G. D., 1986, Cretaceous-Tertiary dinosaur extinction: Science, v. 234, p. 1170-1171.}"
}

@misc{crutzen1987acid5,
    author = "Crutzen, P",
    title = "Acid rain at the K/T boundry",
    year = "1987",
    howpublished = "Nature, v. 330, p. 108-109",
    note = "talkorigins\_source = {true}; raw\_reference = {Crutzen, P., 1987, Acid rain at the K/T boundry: Nature, v. 330, p. 108-109.}"
}

@article{doi101038326143a0,
    author = "Officer, Charles B. and Hallam, Anthony and Drake, Charles L. and Devine, Joseph D.",
    title = "Late Cretaceous and paroxysmal Cretaceous/Tertiary extinctions",
    year = "1987",
    journal = "Nature",
    url = "https://doi.org/10.1038/326143a0",
    doi = "10.1038/326143a0",
    openalex = "W1976899479",
    references = "alvarez1980extraterrestrial, archibald1982upper, doi1010160012821x86901184, doi1010160031018284900944, doi101017s0094837300008071, doi101029jb089ib07p06309, doi101126science1483667220, doi101126science20844481095, doi101126science22346411135, doi101126science2244651867, doi101126science22746911161, doi101126science2314739714, doi101126science2314741979, doi10113000167606197788367ucmsag20co2, doi101130001676061978891389rbeass20co2, doi10113000917613198210153ucbamh20co2, doi101139v74233, doi101146annurevea07050179001115, doi101146annurevea12050184001225, doi1023074156, montanari1986spherules, openalexw2993787886, sloan1986gradual"
}

@incollection{leahy1987the7,
    author = "Leahy, G. D",
    editor = "Currie, P. J. and Koster, E.",
    title = "The Gradual Extinction of Dinosaurs: Fact of Artifact?",
    year = "1987",
    booktitle = "Fourth Symposium on Mesozoic Terrestrial Ecosystems",
    publisher = "Drumheller, Canada, Tyrrell Museum, p. 138-143",
    note = "talkorigins\_source = {true}; raw\_reference = {Leahy, G. D., 1987, The Gradual Extinction of Dinosaurs: Fact of Artifact?, in Currie, P. J., and Koster, E., eds., Fourth Symposium on Mesozoic Terrestrial Ecosystems: Drumheller, Canada, Tyrrell Museum, p. 138-143.}"
}

@misc{officer1987late11,
    author = "Officer, C. B. et al",
    title = "Late Cretaceous and paroxysmal Cretaceous/Tertiary extinctions",
    year = "1987",
    howpublished = "Nature, v. 326, p. 143-149",
    note = "talkorigins\_source = {true}; raw\_reference = {Officer, C. B. et al., 1987, Late Cretaceous and paroxysmal Cretaceous/Tertiary extinctions: Nature, v. 326, p. 143-149.}"
}

@misc{alvarez1990iridium2,
    author = "Alvarez, W. and Asaro, F. and Montanari, A",
    title = "Iridium profile for 10 million years across the Cretaceous-Tertiary boundary at Gubbio (Italy)",
    year = "1990",
    howpublished = "Science, v. 250, no. 4988, p. 1700-1702",
    note = "talkorigins\_source = {true}; raw\_reference = {Alvarez, W., Asaro, F., and Montanari, A., 1990, Iridium profile for 10 million years across the Cretaceous-Tertiary boundary at Gubbio (Italy): Science, v. 250, no. 4988, p. 1700-1702.}"
}

The marker bed at the Cretaceous-Tertiary boundary of the Beloc Formation (southern Haiti) contains abundant coarse-grained microtektites and minor amounts of shocked quartz grains in the basal part. The upper part is composed of medium-grained marl with amalgamated microtektite lenses and finer-grained marl lenses disseminated throughout. Field and petrographic observations, and the distribution of planktonic foraminifera suggest that the bed formed from a complex sequence of events. A bolide impact nearby produced microtektites that sett1led to form a nearly pure layer at the base. Vaporized materials with anomalously high extraterrestrial components settled last, along with carbonate sediments. The entire bed became sparsely consolidated. Subsequently, another major disruptive event, perhaps a giant tsunami, partly reworked the initial deposit. Cohesive fragments of the original marker bed mixed with exotic materials were redeposited as lenticular bodies. This process also may have caused further mixing of Cretaceous and Tertiary microfossils, as observed at Beloc and elsewhere.

@article{doi101126science25250131690,
    author = "Maurrasse, F. J. and Sen, Gautam",
    title = "Impacts, Tsunamis, and the Haitian Cretaceous-Tertiary Boundary Layer",
    year = "1991",
    journal = "Science",
    abstract = "The marker bed at the Cretaceous-Tertiary boundary of the Beloc Formation (southern Haiti) contains abundant coarse-grained microtektites and minor amounts of shocked quartz grains in the basal part. The upper part is composed of medium-grained marl with amalgamated microtektite lenses and finer-grained marl lenses disseminated throughout. Field and petrographic observations, and the distribution of planktonic foraminifera suggest that the bed formed from a complex sequence of events. A bolide impact nearby produced microtektites that sett1led to form a nearly pure layer at the base. Vaporized materials with anomalously high extraterrestrial components settled last, along with carbonate sediments. The entire bed became sparsely consolidated. Subsequently, another major disruptive event, perhaps a giant tsunami, partly reworked the initial deposit. Cohesive fragments of the original marker bed mixed with exotic materials were redeposited as lenticular bodies. This process also may have caused further mixing of Cretaceous and Tertiary microfossils, as observed at Beloc and elsewhere.",
    url = "https://doi.org/10.1126/science.252.5013.1690",
    doi = "10.1126/science.252.5013.1690",
    openalex = "W1973143059",
    references = "alvarez1980extraterrestrial, doi101007springerreference4923, doi1010160025322770900010, doi1010160377839888900059, doi101029jb093ib05p04279, doi101029jb094ib12p17465, doi101038343251a0, doi101086625710, doi101126science2414865567, doi101130spe190p305, doi101144pygs3511, openalexw1570283708"
}

(40)Ar/(39)Ar dating of drill core samples of a glassy melt rock recovered from beneath a massive impact breccia contained within the 180-kilometer subsurface Chicxulub crater in Yucatán, Mexico, has yielded well-behaved incremental heating spectra with a mean plateau age of 64.98 +/- 0.05 million years ago (Ma). The glassy melt rock of andesitic composition was obtained from core 9 (1390 to 1393 meters) in the Chicxulub 1 well. The age of the melt rock is virtually indistinguishable from (40)Ar/(39)Ar ages obtained on tektite glass from Beloc, Haiti, and Arroyo el Mimbral, northeastern Mexico, of 65.01 +/- 0.08 Ma (mean plateau age for Beloc) and 65.07 +/- 0.10 Ma (mean total fusion age for both sites). The (40)Ar/(39)Ar ages, in conjunction with geochemical and petrological similarities, strengthen the recent suggestion that the Chicxulub structure is the source for the Haitian and Mexican tektites and is a viable candidate for the Cretaceous-Tertiary boundary impact site.

@article{doi101126science2575072954,
    author = "Swisher, Carl C. and Grajales-Nishimura, José Manuel and Montanari, Alessandro and Margolis, Stanley V. and Claeys, Philippe and Álvarez, Walter and Renne, Paul R. and Cedillo-Pardoa, Esteban and Maurrasse, F. J. and Curtis, Garniss H. and Smit, Jan and McWilliams, Michael",
    title = "Coeval 40 Ar/ 39 Ar Ages of 65.0 Million Years Ago from Chicxulub Crater Melt Rock and Cretaceous-Tertiary Boundary Tektites",
    year = "1992",
    journal = "Science",
    abstract = "(40)Ar/(39)Ar dating of drill core samples of a glassy melt rock recovered from beneath a massive impact breccia contained within the 180-kilometer subsurface Chicxulub crater in Yucatán, Mexico, has yielded well-behaved incremental heating spectra with a mean plateau age of 64.98 +/- 0.05 million years ago (Ma). The glassy melt rock of andesitic composition was obtained from core 9 (1390 to 1393 meters) in the Chicxulub 1 well. The age of the melt rock is virtually indistinguishable from (40)Ar/(39)Ar ages obtained on tektite glass from Beloc, Haiti, and Arroyo el Mimbral, northeastern Mexico, of 65.01 +/- 0.08 Ma (mean plateau age for Beloc) and 65.07 +/- 0.10 Ma (mean total fusion age for both sites). The (40)Ar/(39)Ar ages, in conjunction with geochemical and petrological similarities, strengthen the recent suggestion that the Chicxulub structure is the source for the Haitian and Mexican tektites and is a viable candidate for the Cretaceous-Tertiary boundary impact site.",
    url = "https://doi.org/10.1126/science.257.5072.954",
    doi = "10.1126/science.257.5072.954",
    openalex = "W2087549641",
    references = "doi1010160012821x77900607, doi1010160016703777901843, doi101016016896228790025x, doi101126science25250131690, doi101126science2535016176, doi1011300091761319910190867ccapct23co2, doi1011300091761319920200099tbdwcu23co2, doi1015159781400862924, doi10151597814008629241, doi102475ajs2622145, openalexw1586251589"
}

Mass extinctions are recognized through the study of fossil groups across event horizons, and from analyses of long-term trends in taxonomic richness and diversity. Both approaches have inherent flaws, and data that once seemed reliable can be readily superseded by the discovery of new fossils and/or the application of new analytical techniques. Herein the current state of the Cretaceous-Tertiary (K-T) biostratigraphical record is reviewed for most major fossil clades, including: calcareous nannoplankton, dinoflagellates, diatoms, radiolaria, foraminifera, ostracodes, scleractinian corals, bryozoans, brachio-pods, molluscs, echinoderms, fish, amphibians, reptiles and terrestrial plants (macrofossils and palynomorphs). These reviews take account of possible biasing factors in the fossil record in order to extract the most comprehensive picture of the K-T biotic crisis available. Results suggest that many faunal and floral groups (ostracodes, bryozoa, ammonite cephalopods, bivalves, archosaurs) were in decline throughout the latest Maastrichtian while others (diatoms, radiolaria, benthic foraminifera, brachiopods, gastropods, fish, amphibians, lepidosaurs, terrestrial plants) passed through the K-T event horizon with only minor taxonomic richness and/or diversity changes. A few microfossil groups (calcareous nannoplankton, dinoflagellates, planktonic foraminifera) did experience a turnover of varying magnitudes in the latest Maastrichtian-earliest Danian. However, many of these turnovers, along with changes in ecological dominance patterns among benthic foraminifera, began in the latest Maastrichtian. Improved taxonomic estimates of the overall pattern and magnitude of the K-T extinction event must await the development of more reliable systematic and phylogenetic data for all Upper Cretaceous clades.

@article{doi101144gsjgs15420265,
    author = "MacLeod, Norman and Rawson, Peter F. and Forey, Peter L. and Banner, F. T. and BouDagher‐Fadel, Marcelle K. and Bown, Paul R. and Burnett, J. A. and Chambers, Paul and Culver, Stephen J. and Evans, Susan E. and Jeffery, C. S. and Kaminski, Michael A. and Lord, Alan and MILNER, A. C. and Milner, Andrew R. and Morris, Noel J. and Owen, Ellie and Rosen, Brian and Smith, A. B. and Taylor, Paul D. and Urquhart, Elspeth and Young, J. R.",
    title = "The Cretaceous-Tertiary biotic transition",
    year = "1997",
    journal = "Journal of the Geological Society",
    abstract = "Mass extinctions are recognized through the study of fossil groups across event horizons, and from analyses of long-term trends in taxonomic richness and diversity. Both approaches have inherent flaws, and data that once seemed reliable can be readily superseded by the discovery of new fossils and/or the application of new analytical techniques. Herein the current state of the Cretaceous-Tertiary (K-T) biostratigraphical record is reviewed for most major fossil clades, including: calcareous nannoplankton, dinoflagellates, diatoms, radiolaria, foraminifera, ostracodes, scleractinian corals, bryozoans, brachio-pods, molluscs, echinoderms, fish, amphibians, reptiles and terrestrial plants (macrofossils and palynomorphs). These reviews take account of possible biasing factors in the fossil record in order to extract the most comprehensive picture of the K-T biotic crisis available. Results suggest that many faunal and floral groups (ostracodes, bryozoa, ammonite cephalopods, bivalves, archosaurs) were in decline throughout the latest Maastrichtian while others (diatoms, radiolaria, benthic foraminifera, brachiopods, gastropods, fish, amphibians, lepidosaurs, terrestrial plants) passed through the K-T event horizon with only minor taxonomic richness and/or diversity changes. A few microfossil groups (calcareous nannoplankton, dinoflagellates, planktonic foraminifera) did experience a turnover of varying magnitudes in the latest Maastrichtian-earliest Danian. However, many of these turnovers, along with changes in ecological dominance patterns among benthic foraminifera, began in the latest Maastrichtian. Improved taxonomic estimates of the overall pattern and magnitude of the K-T extinction event must await the development of more reliable systematic and phylogenetic data for all Upper Cretaceous clades.",
    url = "https://doi.org/10.1144/gsjgs.154.2.0265",
    doi = "10.1144/gsjgs.154.2.0265",
    openalex = "W2111194718",
    references = "alvarez1980extraterrestrial, doi1010160377839888900023, doi101017s0022336000029486, doi101017s0022336000061321, doi101017s0022336000062223, doi101073pnas813801, doi101111j136531211990tb00103x, doi101126science20844481095, doi101126science23547931156, doi1011300016760619951071164mlccot23co2, doi101130spe190p291, doi1012019781003077831, doi102110pec9504, doi102110pec95040129, doi1023071483846, doi1023072259561, doi1023073514632, kier1974evolutionary, kitchell1986biological, kitchellNonebiological, openalexw1599677799, sloan1986gradual"
}

High-precision mass spectrometric analysis of chromium in sediment samples from the Cretaceous-Tertiary (K-T) boundary coincident with the extinction of numerous organisms on Earth confirms the cosmic origin of the K-T phenomenon. The isotopic composition of chromium in K-T boundary samples from Stevns Klint, Denmark, and Caravaca, Spain, is different from that of Earth and indicates its extraterrestrial source. The chromium isotopic signature is consistent with a carbonaceous chondrite-type impactor. The observed differences in the chromium isotopic composition among various meteorite classes can serve as a diagnostic tool for deciphering the nature of impactors that have collided with Earth during its history.

@article{doi101126science2825390927,
    author = "Shukolyukov, A. and Lugmair, G. W.",
    title = "Isotopic Evidence for the Cretaceous-Tertiary Impactor and Its Type",
    year = "1998",
    journal = "Science",
    abstract = "High-precision mass spectrometric analysis of chromium in sediment samples from the Cretaceous-Tertiary (K-T) boundary coincident with the extinction of numerous organisms on Earth confirms the cosmic origin of the K-T phenomenon. The isotopic composition of chromium in K-T boundary samples from Stevns Klint, Denmark, and Caravaca, Spain, is different from that of Earth and indicates its extraterrestrial source. The chromium isotopic signature is consistent with a carbonaceous chondrite-type impactor. The observed differences in the chromium isotopic composition among various meteorite classes can serve as a diagnostic tool for deciphering the nature of impactors that have collided with Earth during its history.",
    url = "https://doi.org/10.1126/science.282.5390.927",
    doi = "10.1126/science.282.5390.927",
    openalex = "W1964355271",
    references = "doi101126science23848311237, doi101146annurevea07050179001115"
}

▪ Abstract The Chicxulub crater ejecta stratigraphy is reviewed, in the context of the stratigraphy of underlying and overlying rock sequences. The ejecta sequence is regionally grouped in (a) thick polymict and monomict breccia sequences inside the crater and within 300 km from the rim of the crater known from drill holes in and close to the breater, and exposures near the border of Yucatan and Belize; (b) Gulf of Mexico region, <2500 m from the crater, with up to 9 m thick, complex, tsunami-wave influenced, tektite-bearing sequences in shallow marine (<500 m deep) environments and tektite bearing, decimeter thick gravity-flow deposits in deep water sites; (c) an intermediate region between 2500 and 4000 km from the crater where centimeter thick, tektite-bearing layers occur, and (d) a global distal region with a millimeter thin ejecta layer. The distal ejecta layer is characterized by sub-millimeter sized microkrystites, often rich in Ni-rich spinels and (altered) clinopyroxene. Wherever present, the ejecta layers mark exactly the sudden mass-mortality horizon of the K/T boundary. What exactly caused the mass mortality is still uncertain, but it appears the main event leading to the K/T mass extinctions.

@article{doi101146annurevearth27175,
    author = "Smit, Jan",
    title = "THE GLOBAL STRATIGRAPHY OF THE CRETACEOUS-TERTIARY BOUNDARY IMPACT EJECTA",
    year = "1999",
    journal = "Annual Review of Earth and Planetary Sciences",
    abstract = "▪ Abstract The Chicxulub crater ejecta stratigraphy is reviewed, in the context of the stratigraphy of underlying and overlying rock sequences. The ejecta sequence is regionally grouped in (a) thick polymict and monomict breccia sequences inside the crater and within 300 km from the rim of the crater known from drill holes in and close to the breater, and exposures near the border of Yucatan and Belize; (b) Gulf of Mexico region, <2500 m from the crater, with up to 9 m thick, complex, tsunami-wave influenced, tektite-bearing sequences in shallow marine (<500 m deep) environments and tektite bearing, decimeter thick gravity-flow deposits in deep water sites; (c) an intermediate region between 2500 and 4000 km from the crater where centimeter thick, tektite-bearing layers occur, and (d) a global distal region with a millimeter thin ejecta layer. The distal ejecta layer is characterized by sub-millimeter sized microkrystites, often rich in Ni-rich spinels and (altered) clinopyroxene. Wherever present, the ejecta layers mark exactly the sudden mass-mortality horizon of the K/T boundary. What exactly caused the mass mortality is still uncertain, but it appears the main event leading to the K/T mass extinctions.",
    url = "https://doi.org/10.1146/annurev.earth.27.1.75",
    doi = "10.1146/annurev.earth.27.1.75",
    openalex = "W2116735545",
    references = "doi1010160012821x9090115e, doi1010160012821x9190113v, doi101126science2244651867, doi101126science25250131690, doi101126science2575072954, doi1011300091761319910190867ccapct23co2, doi1011300091761319920200099tbdwcu23co2, doi102110pec74200094"
}

The devastating effect on terrestrial plant communities of a bolide impact at the Cretaceous-Tertiary boundary is shown in fossil pollen and spore assemblages by a diverse flora being abruptly replaced by one dominated by a few species of fern. Well documented in North America, this fern spike signals widespread deforestation due to an impact winter or massive wildfires. A Southern Hemisphere record of a fern spike, together with a large iridium anomaly, indicates that the devastation was truly global. Recovery of New Zealand plant communities followed a pattern consistent with major climatic perturbations occurring after an impact winter that was possibly preceded by global wildfires.

@article{doi101126science1064706,
    author = "Vajda, Vivi and Raine, J. Ian and Hollis, Christopher J.",
    title = "Indication of Global Deforestation at the Cretaceous-Tertiary Boundary by New Zealand Fern Spike",
    year = "2001",
    journal = "Science",
    abstract = "The devastating effect on terrestrial plant communities of a bolide impact at the Cretaceous-Tertiary boundary is shown in fossil pollen and spore assemblages by a diverse flora being abruptly replaced by one dominated by a few species of fern. Well documented in North America, this fern spike signals widespread deforestation due to an impact winter or massive wildfires. A Southern Hemisphere record of a fern spike, together with a large iridium anomaly, indicates that the devastation was truly global. Recovery of New Zealand plant communities followed a pattern consistent with major climatic perturbations occurring after an impact winter that was possibly preceded by global wildfires.",
    url = "https://doi.org/10.1126/science.1064706",
    doi = "10.1126/science.1064706",
    openalex = "W2073161320",
    references = "doi10102997je01743, doi101038323253a0, doi101038324148a0, doi101038334665a0, doi101038343251a0, doi101038352420a0, doi101126science22546661030, doi101126science2304722167, doi105962bhltitle60647, openalexw1555522030"
}

@incollection{crossref2002xii,
    title = "XII. Dinosaurs and the Cretaceous-Tertiary Extinction",
    year = "2002",
    booktitle = "Disturbing the Solar System",
    url = "https://doi.org/10.1515/9780691239460-014",
    doi = "10.1515/9780691239460-014",
    openalex = "W4205126098",
    pages = "167-182"
}

@incollection{hotton2002palynology,
    author = "Hotton, Carol L.",
    title = "Palynology of the Cretaceous-Tertiary boundary in central Montana: Evidence for extraterrestrial impact as a cause of the terminal Cretaceous extinctions",
    year = "2002",
    booktitle = "The Hell Creek Formation and the Cretaceous-Tertiary boundary in the northern Great Plains: An Integrated continental record of the end of the Cretaceous",
    url = "https://doi.org/10.1130/0-8137-2361-2.473",
    doi = "10.1130/0-8137-2361-2.473",
    openalex = "W2479635556"
}

We present a quantitative analysis of megafloral turnover across the Cretaceous/Paleogene boundary (K/T) based on the most complete record, which comes from the Williston Basin in southwestern North Dakota. More than 22,000 specimens of 353 species have been recovered from 161 localities in a stratigraphic section that is continuous across and temporally calibrated to the K/T and two paleomagnetic reversals. Floral composition changes dynamically during the Cretaceous, shifts sharply at the K/T, and is virtually static during the Paleocene. The K/T is associated with the loss of nearly all dominant species, a significant drop in species richness, and no subsequent recovery. Only 29 of 130 Cretaceous species that appear in more than one stratigraphic level (non-singletons) cross the K/T. Only 11 non-singletons appear first during the Paleocene. The survivors, most of which were minor elements of Cretaceous floras, dominate the impoverished Paleocene floras. Confidence intervals show that the range terminations of most Cretaceous plant taxa are well sampled. We infer that nearly all species with last appearances more than about 5 m below (approximately 70 Kyr before) the K/T truly disappeared before the boundary because of normal turnover dynamics and climate changes; these species should not be counted as K/T victims. Maxima of last appearances occur from 5 to 3 m below the K/T. Interpretation of these last appearances at a fine stratigraphic scale is problematic because of local facies changes, and megafloral data alone, even with confidence intervals, are not sufficient for precise location of an extinction horizon. For this purpose, we rely on high-resolution palynological data previously recovered from continuous facies in the same sections; these place a major plant extinction event precisely at the K/T impact horizon. Accordingly, we interpret the significant cluster of last appearances less than 5 m below the K/T as the signal of a real extinction at the K/T that is recorded slightly down section. A maximum estimate of plant extinction, based on species lost that were present in the uppermost 5 m of Cretaceous strata, is 57%. Palynological data, with higher stratigraphic but lower taxonomic resolution than the megafloral results, provide a minimum estimate of a 30% extinction. The 57% estimate is significantly lower than previous megafloral observations, but these were based on a larger thickness of latest Cretaceous strata, including most of a globally warm interval, and were less sensitive to turnover before the K/T. The loss of one-third to three-fifths of plant species supports a scenario of sudden ecosystem collapse, presumably caused by the Chicxulub impact.

@article{doi1016660094837320040300347lpeate20co2,
    author = "Wilf, Peter and Johnson, Kirk R.",
    title = "Land plant extinction at the end of the Cretaceous: a quantitative analysis of the North Dakota megafloral record",
    year = "2004",
    journal = "Paleobiology",
    abstract = "We present a quantitative analysis of megafloral turnover across the Cretaceous/Paleogene boundary (K/T) based on the most complete record, which comes from the Williston Basin in southwestern North Dakota. More than 22,000 specimens of 353 species have been recovered from 161 localities in a stratigraphic section that is continuous across and temporally calibrated to the K/T and two paleomagnetic reversals. Floral composition changes dynamically during the Cretaceous, shifts sharply at the K/T, and is virtually static during the Paleocene. The K/T is associated with the loss of nearly all dominant species, a significant drop in species richness, and no subsequent recovery. Only 29 of 130 Cretaceous species that appear in more than one stratigraphic level (non-singletons) cross the K/T. Only 11 non-singletons appear first during the Paleocene. The survivors, most of which were minor elements of Cretaceous floras, dominate the impoverished Paleocene floras. Confidence intervals show that the range terminations of most Cretaceous plant taxa are well sampled. We infer that nearly all species with last appearances more than about 5 m below (approximately 70 Kyr before) the K/T truly disappeared before the boundary because of normal turnover dynamics and climate changes; these species should not be counted as K/T victims. Maxima of last appearances occur from 5 to 3 m below the K/T. Interpretation of these last appearances at a fine stratigraphic scale is problematic because of local facies changes, and megafloral data alone, even with confidence intervals, are not sufficient for precise location of an extinction horizon. For this purpose, we rely on high-resolution palynological data previously recovered from continuous facies in the same sections; these place a major plant extinction event precisely at the K/T impact horizon. Accordingly, we interpret the significant cluster of last appearances less than 5 m below the K/T as the signal of a real extinction at the K/T that is recorded slightly down section. A maximum estimate of plant extinction, based on species lost that were present in the uppermost 5 m of Cretaceous strata, is 57\%. Palynological data, with higher stratigraphic but lower taxonomic resolution than the megafloral results, provide a minimum estimate of a 30\% extinction. The 57\% estimate is significantly lower than previous megafloral observations, but these were based on a larger thickness of latest Cretaceous strata, including most of a globally warm interval, and were less sensitive to turnover before the K/T. The loss of one-third to three-fifths of plant species supports a scenario of sudden ecosystem collapse, presumably caused by the Chicxulub impact.",
    url = "https://doi.org/10.1666/0094-8373(2004)030<0347:lpeate>2.0.co;2",
    doi = "10.1666/0094-8373(2004)030<0347:lpeate>2.0.co;2",
    openalex = "W2139973323",
    references = "doi101126science21445271341, doi101126science2314739714, hotton2002palynology"
}

A quantitative scale for measuring greatness, G, of mass extinctions is proposed on the basis of rate of biodiversity diminution expressed as the product of the loss of biodiversity, called magnitude (M), and the inverse of time in which that loss occurs, designated as intensity (I). On this scale, the catastrophic Cretaceous-Tertiary (K-T) extinction appears as the greatest since the Ordovician and the only one with a probable extraterrestrial cause. The end-Permian extinction was less great but with a large magnitude (M) and smaller intensity (I); only some of its individual episodes involved some semblance of catastrophe. Other extinctions during the Phanerozoic, with the possible exception of the end-Silurian diversity plunge, were parts of a forced oscillatory phenomenon and seem caused by marine- and land-habitat destruction during continental assemblies that led to elimination of shelves and (after the Devonian) rain forests and enlargement of deserts. Glaciations and orogenies that shortened and thickened the continental crust only exacerbated these effects. During the Mesozoic and Cainozoic, the evolution of life was linearly progressive, interrupted catastrophically only at the K-T boundary. The end-Triassic extinction was more like the Paleozoic extinctions in nature and probably also in its cause. By contrast, the current extinction resembles none of the earlier ones and may end up being the greatest of all.

@article{doi101073pnas0805482105,
    author = "Sengör, A M Celâl and Atayman, Saniye and Ozeren, Sinan",
    title = "A scale of greatness and causal classification of mass extinctions: implications for mechanisms.",
    year = "2008",
    journal = "Proceedings of the National Academy of Sciences of the United States of America",
    abstract = "A quantitative scale for measuring greatness, G, of mass extinctions is proposed on the basis of rate of biodiversity diminution expressed as the product of the loss of biodiversity, called magnitude (M), and the inverse of time in which that loss occurs, designated as intensity (I). On this scale, the catastrophic Cretaceous-Tertiary (K-T) extinction appears as the greatest since the Ordovician and the only one with a probable extraterrestrial cause. The end-Permian extinction was less great but with a large magnitude (M) and smaller intensity (I); only some of its individual episodes involved some semblance of catastrophe. Other extinctions during the Phanerozoic, with the possible exception of the end-Silurian diversity plunge, were parts of a forced oscillatory phenomenon and seem caused by marine- and land-habitat destruction during continental assemblies that led to elimination of shelves and (after the Devonian) rain forests and enlargement of deserts. Glaciations and orogenies that shortened and thickened the continental crust only exacerbated these effects. During the Mesozoic and Cainozoic, the evolution of life was linearly progressive, interrupted catastrophically only at the K-T boundary. The end-Triassic extinction was more like the Paleozoic extinctions in nature and probably also in its cause. By contrast, the current extinction resembles none of the earlier ones and may end up being the greatest of all.",
    url = "https://pmc.ncbi.nlm.nih.gov/articles/PMC2544523/",
    doi = "10.1073/pnas.0805482105",
    openalex = "W2067988424",
    pmcid = "PMC2544523",
    pmid = "18779562",
    references = "alvarez1980extraterrestrial, doi10100797894017960024, doi101017s0094837300003778, doi101029gm100, doi101093oso97801985491780010001, doi101126science21545391501, doi1023073515466, doi105860choice435903, doi105962bhltitle50860, doi107312webb12678"
}

The present paper completes a restudy of the main lava pile in the Deccan flood basalt province (trap) of India. Chenet et al. (2008) reported results from the upper third, and this paper reports the lower two thirds of the 3500‐m‐thick composite section. The methods employed are the same, i.e., combined use of petrology, volcanology, chemostratigraphy, morphology, K‐Ar absolute dating, study of sedimentary alteration horizons, and as the main correlation tool, analysis of detailed paleomagnetic remanence directions. The thickness and volume of the flood basalt province studied in this way are therefore tripled. A total of 169 sites from eight new sections are reported in this paper. Together with the results of Chenet et al. (2008), these data represent in total 70% of the 3500‐m combined section of the main Deccan traps province. This lava pile was erupted in some 30 major eruptive periods or single eruptive events (SEE), each with volumes ranging from 1000 to 20,000 km 3 and 41 individual lava units with a typical volume of 1300 km 3. Paleomagnetic analysis shows that some SEEs with thicknesses attaining 200 m were emplaced over distances in excess of 100 km (both likely underestimates, due to outcrop conditions) and up to 800 km. The total time of emission of all combined SEEs could have been (much) less than 10 ka, with most of the time recorded in a very small number of intervening alteration levels marking periods of volcanic quiescence (so‐called “big red boles”). The number of boles, thickness of the pulses, and morphology of the traps suggest that eruptive fluxes and volumes were larger in the older formations and slowed down with more and longer quiescence periods in the end. On the basis of geochronologic results published by Chenet et al. (2007) and paleontological results from Keller et al. (2008), we propose that volcanism occurred in three rather short, discrete phases or megapulses, an early one at ∼67.5 ± 1 Ma near the C30r/C30n transition and the two largest around 65 ± 1 Ma, one entirely within C29r just before the K‐T boundary, the other shortly afterward spanning the C29r/C29n reversal. We next estimate sulfur dioxide (likely a major agent of environmental stress) amounts and fluxes released by SEEs: they would have ranged from 5 to 100 Gt and 0.1 to 1 Gt/a, respectively, over durations possibly as short as 100 years for each SEE. The chemical input of the Chicxulub impact would have been on the same order as that of a very large single pulse. The impact, therefore, appears as important but incremental, neither the sole nor main cause of the Cretaceous‐Tertiary mass extinctions.

@article{doi1010292008jb005644,
    author = "Chenet, A. and Courtillot, Vincent and Fluteau, Frédéric and Gérard, Martine and Quidelleur, Xavier and Khadri, S. and Subbarao, Κ. V. and Thórdarson, T.",
    title = "Determination of rapid Deccan eruptions across the Cretaceous‐Tertiary boundary using paleomagnetic secular variation: 2. Constraints from analysis of eight new sections and synthesis for a 3500‐m‐thick composite section",
    year = "2009",
    journal = "Journal of Geophysical Research Atmospheres",
    abstract = "The present paper completes a restudy of the main lava pile in the Deccan flood basalt province (trap) of India. Chenet et al. (2008) reported results from the upper third, and this paper reports the lower two thirds of the 3500‐m‐thick composite section. The methods employed are the same, i.e., combined use of petrology, volcanology, chemostratigraphy, morphology, K‐Ar absolute dating, study of sedimentary alteration horizons, and as the main correlation tool, analysis of detailed paleomagnetic remanence directions. The thickness and volume of the flood basalt province studied in this way are therefore tripled. A total of 169 sites from eight new sections are reported in this paper. Together with the results of Chenet et al. (2008), these data represent in total 70\% of the 3500‐m combined section of the main Deccan traps province. This lava pile was erupted in some 30 major eruptive periods or single eruptive events (SEE), each with volumes ranging from 1000 to 20,000 km 3 and 41 individual lava units with a typical volume of 1300 km 3. Paleomagnetic analysis shows that some SEEs with thicknesses attaining 200 m were emplaced over distances in excess of 100 km (both likely underestimates, due to outcrop conditions) and up to 800 km. The total time of emission of all combined SEEs could have been (much) less than 10 ka, with most of the time recorded in a very small number of intervening alteration levels marking periods of volcanic quiescence (so‐called “big red boles”). The number of boles, thickness of the pulses, and morphology of the traps suggest that eruptive fluxes and volumes were larger in the older formations and slowed down with more and longer quiescence periods in the end. On the basis of geochronologic results published by Chenet et al. (2007) and paleontological results from Keller et al. (2008), we propose that volcanism occurred in three rather short, discrete phases or megapulses, an early one at ∼67.5 ± 1 Ma near the C30r/C30n transition and the two largest around 65 ± 1 Ma, one entirely within C29r just before the K‐T boundary, the other shortly afterward spanning the C29r/C29n reversal. We next estimate sulfur dioxide (likely a major agent of environmental stress) amounts and fluxes released by SEEs: they would have ranged from 5 to 100 Gt and 0.1 to 1 Gt/a, respectively, over durations possibly as short as 100 years for each SEE. The chemical input of the Chicxulub impact would have been on the same order as that of a very large single pulse. The impact, therefore, appears as important but incremental, neither the sole nor main cause of the Cretaceous‐Tertiary mass extinctions.",
    url = "https://doi.org/10.1029/2008jb005644",
    doi = "10.1029/2008jb005644",
    openalex = "W2066351018",
    references = "doi1010160012821x86901184, doi101016jepsl200801015, doi101016s0012825200000374, doi101016s1631071303000063, doi1010292000jb000050, doi10102994jb03098, doi10108008120090500170393, doi101098rspa19530064, doi101111j1365246x1980tb02601x, openalexw1520428197, openalexw1575579655, openalexw2974218786"
}

The Cretaceous-Paleogene boundary approximately 65.5 million years ago marks one of the three largest mass extinctions in the past 500 million years. The extinction event coincided with a large asteroid impact at Chicxulub, Mexico, and occurred within the time of Deccan flood basalt volcanism in India. Here, we synthesize records of the global stratigraphy across this boundary to assess the proposed causes of the mass extinction. Notably, a single ejecta-rich deposit compositionally linked to the Chicxulub impact is globally distributed at the Cretaceous-Paleogene boundary. The temporal match between the ejecta layer and the onset of the extinctions and the agreement of ecological patterns in the fossil record with modeled environmental perturbations (for example, darkness and cooling) lead us to conclude that the Chicxulub impact triggered the mass extinction.

@article{doi101126science1177265,
    author = "Schulte, Peter and Alegret, Laia and Arenillas, Ignacio and Arz, José Antonio and Barton, P. J. and Bown, Paul R. and Bralower, Timothy J. and Christeson, Gail and Claeys, Philippe and Cockell, Charles S. and Collins, G. S. and Deutsch, A. and Goldin, Tamara and Goto, Kazuhisa and Grajales-Nishimura, José Manuel and Grieve, R. A. F. and Gulick, S. P. S. and Johnson, Kirk R. and Kiessling, Wolfgang and Koeberl, Christian and Kring, D. A. and MacLeod, Kenneth G. and Matsui, Takafumi and Melosh, J. and Montanari, Alessandro and Morgan, Joanna and Neal, C. R. and Nichols, Douglas J. and Norris, Richard D. and Pierazzo, E. and Ravizza, Greg and Rebolledo‐Vieyra, M. and Reimold, W. U. and Robin, Éric and Salge, T. and Speijer, Robert P. and Sweet, A R and Urrutia‐Fucugauchi, J. and Vajda, Vivi and Whalen, Michael T. and Willumsen, Pi Suhr",
    title = "The Chicxulub Asteroid Impact and Mass Extinction at the Cretaceous-Paleogene Boundary",
    year = "2010",
    journal = "Science",
    abstract = "The Cretaceous-Paleogene boundary approximately 65.5 million years ago marks one of the three largest mass extinctions in the past 500 million years. The extinction event coincided with a large asteroid impact at Chicxulub, Mexico, and occurred within the time of Deccan flood basalt volcanism in India. Here, we synthesize records of the global stratigraphy across this boundary to assess the proposed causes of the mass extinction. Notably, a single ejecta-rich deposit compositionally linked to the Chicxulub impact is globally distributed at the Cretaceous-Paleogene boundary. The temporal match between the ejecta layer and the onset of the extinctions and the agreement of ecological patterns in the fossil record with modeled environmental perturbations (for example, darkness and cooling) lead us to conclude that the Chicxulub impact triggered the mass extinction.",
    url = "https://doi.org/10.1126/science.1177265",
    doi = "10.1126/science.1177265",
    openalex = "W2160490562",
    references = "alvarez1980extraterrestrial, doi101016jepsl200605041, doi101016jepsl200607020, doi101016jepsl200902019, doi101016jpalaeo200702037, doi101016jpalaeo200709016, doi101017cbo9780511535536, doi1010292008jb005644, doi10102996rg03038, doi10102997je01743, doi101038285198a0, doi101073pnas0802597105, doi101126science1064706, doi101126science20844481095, doi1011300091761319910190867ccapct23co2, doi101130081372356655, doi1011302007242401, doi101146annurevearth27175, doi101146annurevecolsys35021103105715"
}

Previous analyses of relations, divergence times, and diversification patterns among extant mammalian families have relied on supertree methods and local molecular clocks. We constructed a molecular supermatrix for mammalian families and analyzed these data with likelihood-based methods and relaxed molecular clocks. Phylogenetic analyses resulted in a robust phylogeny with better resolution than phylogenies from supertree methods. Relaxed clock analyses support the long-fuse model of diversification and highlight the importance of including multiple fossil calibrations that are spread across the tree. Molecular time trees and diversification analyses suggest important roles for the Cretaceous Terrestrial Revolution and Cretaceous-Paleogene (KPg) mass extinction in opening up ecospace that promoted interordinal and intraordinal diversification, respectively. By contrast, diversification analyses provide no support for the hypothesis concerning the delayed rise of present-day mammals during the Eocene Period.

@article{doi101126science1211028,
    author = "Meredith, Robert W. and Janečka, Jan E. and Gatesy, John and Ryder, Oliver A. and Fisher, Colleen A. and Teeling, Emma C. and Goodbla, Alisha and Eizirik, Eduardo and Simão, Taiz L. L. and Stadler, Tanja and Rabosky, Daniel L. and Honeycutt, Rodney L. and Flynn, John J. and Ingram, Colleen M. and Steiner, Cynthia and Williams, Tiffani L. and Robinson, Terence J. and Burk-Herrick, Angela and Westerman, Michael and Ayoub, Nadia A. and Springer, Mark S. and Murphy, William J.",
    title = "Impacts of the Cretaceous Terrestrial Revolution and KPg Extinction on Mammal Diversification",
    year = "2011",
    journal = "Science",
    abstract = "Previous analyses of relations, divergence times, and diversification patterns among extant mammalian families have relied on supertree methods and local molecular clocks. We constructed a molecular supermatrix for mammalian families and analyzed these data with likelihood-based methods and relaxed molecular clocks. Phylogenetic analyses resulted in a robust phylogeny with better resolution than phylogenies from supertree methods. Relaxed clock analyses support the long-fuse model of diversification and highlight the importance of including multiple fossil calibrations that are spread across the tree. Molecular time trees and diversification analyses suggest important roles for the Cretaceous Terrestrial Revolution and Cretaceous-Paleogene (KPg) mass extinction in opening up ecospace that promoted interordinal and intraordinal diversification, respectively. By contrast, diversification analyses provide no support for the hypothesis concerning the delayed rise of present-day mammals during the Eocene Period.",
    url = "https://doi.org/10.1126/science.1211028",
    doi = "10.1126/science.1211028",
    openalex = "W2140803428",
    references = "doi101016jtree200610002, doi101023a1011317930838, doi101038381226a0, doi101038nature05634, doi101038nature09705, doi101038nature10291, doi101073pnas0334222100, doi101073pnas1016876108, doi101093sysbiosyp031, doi101101gr5918807, doi101126science1067179, doi101353book59141"
}

The Cretaceous-Paleogene (K-Pg) boundary is marked by a major mass extinction, yet this event is thought to have had little effect on the diversity of lizards and snakes (Squamata). A revision of fossil squamates from the Maastrichtian and Paleocene of North America shows that lizards and snakes suffered a devastating mass extinction coinciding with the Chicxulub asteroid impact. Species-level extinction was 83%, and the K-Pg event resulted in the elimination of many lizard groups and a dramatic decrease in morphological disparity. Survival was associated with small body size and perhaps large geographic range. The recovery was prolonged; diversity did not approach Cretaceous levels until 10 My after the extinction, and resulted in a dramatic change in faunal composition. The squamate fossil record shows that the end-Cretaceous mass extinction was far more severe than previously believed, and underscores the role played by mass extinctions in driving diversification.

@article{doi101073pnas1211526110,
    author = "Longrich, Nicholas R. and Bhullar, Bhart‐Anjan S. and Gauthier, Jacques A.",
    title = "Mass extinction of lizards and snakes at the Cretaceous–Paleogene boundary",
    year = "2012",
    journal = "Proceedings of the National Academy of Sciences",
    abstract = "The Cretaceous-Paleogene (K-Pg) boundary is marked by a major mass extinction, yet this event is thought to have had little effect on the diversity of lizards and snakes (Squamata). A revision of fossil squamates from the Maastrichtian and Paleocene of North America shows that lizards and snakes suffered a devastating mass extinction coinciding with the Chicxulub asteroid impact. Species-level extinction was 83\%, and the K-Pg event resulted in the elimination of many lizard groups and a dramatic decrease in morphological disparity. Survival was associated with small body size and perhaps large geographic range. The recovery was prolonged; diversity did not approach Cretaceous levels until 10 My after the extinction, and resulted in a dramatic change in faunal composition. The squamate fossil record shows that the end-Cretaceous mass extinction was far more severe than previously believed, and underscores the role played by mass extinctions in driving diversification.",
    url = "https://doi.org/10.1073/pnas.1211526110",
    doi = "10.1073/pnas.1211526110",
    openalex = "W2003820601",
    references = "alvarez1980extraterrestrial, doi101016jpalaeo201206027, doi101017cbo9780511535536, doi101098rsbl20060523, doi101126science1177265, doi101126science21545391501, doi1015259780520935433, doi101890030557, doi1033740140530101, doi105860choice413447, doi107312kiel11918, openalexw1488067709, openalexw337536883"
}

Nearly all data regarding land-plant turnover across the Cretaceous/Paleogene boundary come from western North America, relatively close to the Chicxulub, Mexico impact site. Here, we present a palynological analysis of a section in Patagonia that shows a marked fall in diversity and abundance of nearly all plant groups across the K/Pg interval. Minimum diversity occurs during the earliest Danian, but only a few palynomorphs show true extinctions. The low extinction rate is similar to previous observations from New Zealand. The differing responses between the Southern and Northern hemispheres could be related to the attenuation of damage with increased distance from the impact site, to hemispheric differences in extinction severity, or to both effects. Legacy effects of the terminal Cretaceous event also provide a plausible, partial explanation for the fact that Paleocene and Eocene macrofloras from Patagonia are among the most diverse known globally. Also of great interest, earliest Danian assemblages are dominated by the gymnosperm palynomorphs Classopollis of the extinct Mesozoic conifer family Cheirolepidiaceae. The expansion of Classopollis after the boundary in Patagonia is another example of typically Mesozoic plant lineages surviving into the Cenozoic in southern Gondwanan areas, and this greatly supports previous hypotheses of high latitude southern regions as biodiversity refugia during the end-Cretaceous global crisis.

@article{doi101371journalpone0052455,
    author = "Barreda, Viviana D. and Cúneo, N. Rubén and Wilf, Peter and Currano, Ellen D. and Scasso, Roberto A. and Brinkhuis, Henk",
    title = "Cretaceous/Paleogene Floral Turnover in Patagonia: Drop in Diversity, Low Extinction, and a Classopollis Spike",
    year = "2012",
    journal = "PLoS ONE",
    abstract = "Nearly all data regarding land-plant turnover across the Cretaceous/Paleogene boundary come from western North America, relatively close to the Chicxulub, Mexico impact site. Here, we present a palynological analysis of a section in Patagonia that shows a marked fall in diversity and abundance of nearly all plant groups across the K/Pg interval. Minimum diversity occurs during the earliest Danian, but only a few palynomorphs show true extinctions. The low extinction rate is similar to previous observations from New Zealand. The differing responses between the Southern and Northern hemispheres could be related to the attenuation of damage with increased distance from the impact site, to hemispheric differences in extinction severity, or to both effects. Legacy effects of the terminal Cretaceous event also provide a plausible, partial explanation for the fact that Paleocene and Eocene macrofloras from Patagonia are among the most diverse known globally. Also of great interest, earliest Danian assemblages are dominated by the gymnosperm palynomorphs Classopollis of the extinct Mesozoic conifer family Cheirolepidiaceae. The expansion of Classopollis after the boundary in Patagonia is another example of typically Mesozoic plant lineages surviving into the Cenozoic in southern Gondwanan areas, and this greatly supports previous hypotheses of high latitude southern regions as biodiversity refugia during the end-Cretaceous global crisis.",
    url = "https://doi.org/10.1371/journal.pone.0052455",
    doi = "10.1371/journal.pone.0052455",
    openalex = "W2148255348",
    references = "alvarez1980extraterrestrial, doi1010160034666782900380, doi101016jrevpalbo200606008, doi101073pnas0905130106, doi101086430055, doi101126science1064706, doi101126science1177265, doi101126science21445271341, doi101126science22546661030, doi1023071942268, doi105860choice293880, hotton2002palynology"
}

For the past three decades, the Alvarez impact theory of mass extinction, causally related to catastrophic meteorite impacts, has been recurrently applied to multiple extinction boundaries. However, these multidisciplinary research efforts across the globe have been largely unsuccessful to date, with one outstanding exception: the Cretaceous-Paleogene boundary. The unicausal impact scenario as a leading explanation, when applied to the complex fossil record, has resulted in force-fitting of data and interpretations ("great expectations syndrome"). The misunderstandings can be grouped at three successive levels of the testing process, and involve the unreflective application of the impact paradigm: (i) factual misidentification, i.e., an erroneous or indefinite recognition of the extraterrestrial record in sedimentological, physical and geochemical contexts, (ii) correlative misinterpretation of the adequately documented impact signals due to their incorrect dating, and (iii) causal overestimation when the proved impact characteristics are doubtful as a sufficient trigger of a contemporaneous global cosmic catastrophe. Examples of uncritical belief in the simple cause-effect scenario for the Frasnian-Famennian, Permian-Triassic, and Triassic-Jurassic (and the Eifelian-Givetian and Paleocene-Eocene as well) global events include mostly item-1 pitfalls (factual misidentification), with Ir enrichments and shocked minerals frequently misidentified. Therefore, these mass extinctions are still at the first test level, and only the F-F extinction is potentially seen in the context of item-2, the interpretative step, because of the possible causative link with the Siljan Ring crater (53 km in diameter). The erratically recognized cratering signature is often marked by large timing and size uncertainties, and item-3, the advanced causal inference, is in fact limited to clustered impacts that clearly predate major mass extinctions. The multi-impact lag-time pattern is particularly clear in the Late Triassic, when the largest (100 km diameter) Manicouagan crater was possibly concurrent with the end-Carnian extinction (or with the late Norian tetrapod turnover on an alternative time scale). The relatively small crater sizes and cratonic (crystalline rock basement) setting of these two craters further suggest the strongly insufficient extraterrestrial trigger of worldwide environmental traumas. However, to discuss the kill potential of impact events in a more robust fashion, their location and timing, vulnerability factors, especially target geology and palaeogeography in the context of associated climate-active volatile fluxes, should to be rigorously assessed. The current lack of conclusive impact evidence synchronous with most mass extinctions may still be somewhat misleading due to the predicted large set of undiscovered craters, particularly in light of the obscured record of oceanic impact events.

@article{doi104202app20110058,
    author = "Racki, Grzegorz",
    title = "The Alvarez Impact Theory of Mass Extinction; Limits to its Applicability and the “Great Expectations Syndrome”",
    year = "2012",
    journal = "Acta Palaeontologica Polonica",
    abstract = {For the past three decades, the Alvarez impact theory of mass extinction, causally related to catastrophic meteorite impacts, has been recurrently applied to multiple extinction boundaries. However, these multidisciplinary research efforts across the globe have been largely unsuccessful to date, with one outstanding exception: the Cretaceous-Paleogene boundary. The unicausal impact scenario as a leading explanation, when applied to the complex fossil record, has resulted in force-fitting of data and interpretations ("great expectations syndrome"). The misunderstandings can be grouped at three successive levels of the testing process, and involve the unreflective application of the impact paradigm: (i) factual misidentification, i.e., an erroneous or indefinite recognition of the extraterrestrial record in sedimentological, physical and geochemical contexts, (ii) correlative misinterpretation of the adequately documented impact signals due to their incorrect dating, and (iii) causal overestimation when the proved impact characteristics are doubtful as a sufficient trigger of a contemporaneous global cosmic catastrophe. Examples of uncritical belief in the simple cause-effect scenario for the Frasnian-Famennian, Permian-Triassic, and Triassic-Jurassic (and the Eifelian-Givetian and Paleocene-Eocene as well) global events include mostly item-1 pitfalls (factual misidentification), with Ir enrichments and shocked minerals frequently misidentified. Therefore, these mass extinctions are still at the first test level, and only the F-F extinction is potentially seen in the context of item-2, the interpretative step, because of the possible causative link with the Siljan Ring crater (53 km in diameter). The erratically recognized cratering signature is often marked by large timing and size uncertainties, and item-3, the advanced causal inference, is in fact limited to clustered impacts that clearly predate major mass extinctions. The multi-impact lag-time pattern is particularly clear in the Late Triassic, when the largest (100 km diameter) Manicouagan crater was possibly concurrent with the end-Carnian extinction (or with the late Norian tetrapod turnover on an alternative time scale). The relatively small crater sizes and cratonic (crystalline rock basement) setting of these two craters further suggest the strongly insufficient extraterrestrial trigger of worldwide environmental traumas. However, to discuss the kill potential of impact events in a more robust fashion, their location and timing, vulnerability factors, especially target geology and palaeogeography in the context of associated climate-active volatile fluxes, should to be rigorously assessed. The current lack of conclusive impact evidence synchronous with most mass extinctions may still be somewhat misleading due to the predicted large set of undiscovered craters, particularly in light of the obscured record of oceanic impact events.},
    url = "https://doi.org/10.4202/app.2011.0058",
    doi = "10.4202/app.2011.0058",
    openalex = "W1991076266",
    references = "alvarez1980extraterrestrial, doi101016jearscirev200811004, doi101016s0031018297000503, doi101038nature10385, doi101073pnas0805482105, doi101093oso97801985491780010001, doi101126science1177265, doi101126science21545391501, doi101126science2895478432, doi1011300091761319910190867ccapct23co2, doi101144gsjgs14650749, doi1023073515466, doi105860choice293880, openalexw2912219260"
}

The Cretaceous/Tertiary (K/Pg) mass extinction has long been viewed as a pivotal event in mammalian evolutionary history, in which the extinction of non-avian dinosaurs allowed mammals to rapidly expand from small-bodied, generalized insectivores to a wide array of body sizes and ecological specializations. Many studies have used global- or continental-scale taxonomic databases to analyze this event on coarse temporal scales, but few studies have documented morphological diversity of mammalian paleocommunities on fine spatiotemporal scales in order to examine ecomorphological selectivity and ecospace filling across this critical transition. Focusing on well-sampled and temporally well-constrained mammalian faunas across the K/Pg boundary in northeastern Montana, I quantified dental-shape disparity and morphospace occupancy via landmark- and semilandmark-based geometric morphometrics and mean body size, body-size disparity, and body-size structure via body-mass estimates. My results reveal several key findings: (1) latest Cretaceous mammals, particularly metatherians and multituberculates, had a greater ecomorphological diversity than is generally appreciated, occupying regions of the morphospace that are interpreted as strict carnivory, plant-dominated omnivory, and herbivory; (2) the decline in dental-shape disparity and body-size disparity across the K/Pg boundary shows a pattern of constructive extinction selectivity against larger-bodied dietary specialists, particularly strict carnivores and taxa with plant-based diets, that suggests the kill mechanism was related to depressed primary productivity rather than a globally instantaneous event; (3) the ecomorphological recovery in the earliest Paleocene was fueled by immigrants, namely three multituberculate families (taeniolabidids, microcosmodontids, eucosmodontids) and to a lesser extent archaic ungulates; and (4) despite immediate increases in the taxonomic richness of eutherians, their much-celebrated post-K/Pg ecomorphological expansion had a slower start than is generally perceived and most likely only began 400,000 to 1 million years after the extinction event.

@article{doi10166612041,
    author = "Wilson, Gregory P.",
    title = "Mammals across the K/Pg boundary in northeastern Montana, U.S.A.: dental morphology and body-size patterns reveal extinction selectivity and immigrant-fueled ecospace filling",
    year = "2013",
    journal = "Paleobiology",
    abstract = "The Cretaceous/Tertiary (K/Pg) mass extinction has long been viewed as a pivotal event in mammalian evolutionary history, in which the extinction of non-avian dinosaurs allowed mammals to rapidly expand from small-bodied, generalized insectivores to a wide array of body sizes and ecological specializations. Many studies have used global- or continental-scale taxonomic databases to analyze this event on coarse temporal scales, but few studies have documented morphological diversity of mammalian paleocommunities on fine spatiotemporal scales in order to examine ecomorphological selectivity and ecospace filling across this critical transition. Focusing on well-sampled and temporally well-constrained mammalian faunas across the K/Pg boundary in northeastern Montana, I quantified dental-shape disparity and morphospace occupancy via landmark- and semilandmark-based geometric morphometrics and mean body size, body-size disparity, and body-size structure via body-mass estimates. My results reveal several key findings: (1) latest Cretaceous mammals, particularly metatherians and multituberculates, had a greater ecomorphological diversity than is generally appreciated, occupying regions of the morphospace that are interpreted as strict carnivory, plant-dominated omnivory, and herbivory; (2) the decline in dental-shape disparity and body-size disparity across the K/Pg boundary shows a pattern of constructive extinction selectivity against larger-bodied dietary specialists, particularly strict carnivores and taxa with plant-based diets, that suggests the kill mechanism was related to depressed primary productivity rather than a globally instantaneous event; (3) the ecomorphological recovery in the earliest Paleocene was fueled by immigrants, namely three multituberculate families (taeniolabidids, microcosmodontids, eucosmodontids) and to a lesser extent archaic ungulates; and (4) despite immediate increases in the taxonomic richness of eutherians, their much-celebrated post-K/Pg ecomorphological expansion had a slower start than is generally perceived and most likely only began 400,000 to 1 million years after the extinction event.",
    url = "https://doi.org/10.1666/12041",
    doi = "10.1666/12041",
    openalex = "W2117661420",
    references = "doi101007978146139249113, doi101007s1091400569434, doi101016c20100662092, doi101029eo067i035p00649, doi101038nature05634, doi101038ncomms1815, doi101126science1177265, doi101126science1211028, doi101126science1483667220, doi1011302014250315, doi101146annurevecolsys281495, doi101371journalpone0025186, doi1023071267862, doi1023073546992, doi102307jctvjsf433, doi105860choice290302, doi105860choice396411, hotton2002palynology, lofgren1990reworking, openalexw610180004"
}

Changes in pollen and spore assemblages across the Cretaceous–Paleogene (K–Pg) boundary elucidate the vegetation response to a global environmental crisis triggered by an asteroid impact in Mexico 66 Ma. The Cretaceous–Paleogene boundary clay, associated with the Chicxulub asteroid impact event, constitutes a unique, global marker bed enabling comparison of the world-wide palynological signal spanning the mass extinction event. The data from both hemispheres are consistent, revealing diverse latest Cretaceous assemblages of pollen and spores that were affected by a major diversity loss as a consequence of the K–Pg event. Here we combine new results with past studies to provide an integrated global perspective of the terrestrial vegetation record across the K–Pg boundary. We further apply the K–Pg event as a template to asses the causal mechanism behind other major events in Earths history. The end-Permian, end-Triassic, and the K–Pg mass-extinctions were responses to different causal processes that resulted in essentially similar succession of decline and recovery phases, although expressed at different temporal scales. The events share a characteristic pattern of a bloom of opportunistic “crisis” tax followed by a pulse in pioneer communities, and finally a recovery in diversity including evolution of new taxa. Based on their similar extinction and recovery patterns and the fact that the Last and First Appearance Datums associated with the extinctions are separated in time, we recommend using the K–Pg event as a model and to use relative abundance data for the stratigraphic definition of mass-extinction events and the placement of associated chronostratigraphic boundaries.

@article{doi101016jgloplacha201407014,
    author = "Vajda, Vivi and Bercovici, Antoine",
    title = "The global vegetation pattern across the Cretaceous–Paleogene mass extinction interval: A template for other extinction events",
    year = "2014",
    journal = "Global and Planetary Change",
    abstract = "Changes in pollen and spore assemblages across the Cretaceous–Paleogene (K–Pg) boundary elucidate the vegetation response to a global environmental crisis triggered by an asteroid impact in Mexico 66 Ma. The Cretaceous–Paleogene boundary clay, associated with the Chicxulub asteroid impact event, constitutes a unique, global marker bed enabling comparison of the world-wide palynological signal spanning the mass extinction event. The data from both hemispheres are consistent, revealing diverse latest Cretaceous assemblages of pollen and spores that were affected by a major diversity loss as a consequence of the K–Pg event. Here we combine new results with past studies to provide an integrated global perspective of the terrestrial vegetation record across the K–Pg boundary. We further apply the K–Pg event as a template to asses the causal mechanism behind other major events in Earths history. The end-Permian, end-Triassic, and the K–Pg mass-extinctions were responses to different causal processes that resulted in essentially similar succession of decline and recovery phases, although expressed at different temporal scales. The events share a characteristic pattern of a bloom of opportunistic “crisis” tax followed by a pulse in pioneer communities, and finally a recovery in diversity including evolution of new taxa. Based on their similar extinction and recovery patterns and the fact that the Last and First Appearance Datums associated with the extinctions are separated in time, we recommend using the K–Pg event as a model and to use relative abundance data for the stratigraphic definition of mass-extinction events and the placement of associated chronostratigraphic boundaries.",
    url = "https://doi.org/10.1016/j.gloplacha.2014.07.014",
    doi = "10.1016/j.gloplacha.2014.07.014",
    openalex = "W2079006768",
    references = "doi101007s1091400569434, doi1010160034666780900226, doi101016jcretres200805030, doi101016jepsl200902019, doi101016jpalaeo200702037, doi101016jpalaeo201105050, doi101017cbo9780511535536, doi101038352420a0, doi101038ncomms1815, doi101073pnas1211526110, doi101073pnas1319253111, doi101073pnas802627, doi101080019161222012718609, doi10108003115517708527763, doi10108011035890902924877, doi101130spe247, doi101371journalpone0052455, doi1023073514678, hotton2002palynology, russell2002synopsis"
}

Non-avian dinosaurs went extinct 66 million years ago, geologically coincident with the impact of a large bolide (comet or asteroid) during an interval of massive volcanic eruptions and changes in temperature and sea level. There has long been fervent debate about how these events affected dinosaurs. We review a wealth of new data accumulated over the past two decades, provide updated and novel analyses of long-term dinosaur diversity trends during the latest Cretaceous, and discuss an emerging consensus on the extinction's tempo and causes. Little support exists for a global, long-term decline across non-avian dinosaur diversity prior to their extinction at the end of the Cretaceous. However, restructuring of latest Cretaceous dinosaur faunas in North America led to reduced diversity of large-bodied herbivores, perhaps making communities more susceptible to cascading extinctions. The abruptness of the dinosaur extinction suggests a key role for the bolide impact, although the coarseness of the fossil record makes testing the effects of Deccan volcanism difficult.

@article{doi101111brv12128,
    author = "Brusatte, Stephen L. and Butler, Richard J. and Barrett, Paul M. and Carrano, Matthew T. and Evans, David C. and Lloyd, Graeme T. and Mannion, Philip D. and Norell, Mark A. and Peppe, Daniel J. and Upchurch, Paul and Williamson, Thomas E.",
    title = "The extinction of the dinosaurs",
    year = "2014",
    journal = "Biological reviews/Biological reviews of the Cambridge Philosophical Society",
    abstract = "Non-avian dinosaurs went extinct 66 million years ago, geologically coincident with the impact of a large bolide (comet or asteroid) during an interval of massive volcanic eruptions and changes in temperature and sea level. There has long been fervent debate about how these events affected dinosaurs. We review a wealth of new data accumulated over the past two decades, provide updated and novel analyses of long-term dinosaur diversity trends during the latest Cretaceous, and discuss an emerging consensus on the extinction's tempo and causes. Little support exists for a global, long-term decline across non-avian dinosaur diversity prior to their extinction at the end of the Cretaceous. However, restructuring of latest Cretaceous dinosaur faunas in North America led to reduced diversity of large-bodied herbivores, perhaps making communities more susceptible to cascading extinctions. The abruptness of the dinosaur extinction suggests a key role for the bolide impact, although the coarseness of the fossil record makes testing the effects of Deccan volcanism difficult.",
    url = "https://doi.org/10.1111/brv.12128",
    doi = "10.1111/brv.12128",
    openalex = "W1515034626",
    references = "alvarez1980extraterrestrial, doi101007s0011400804990, doi101007s1091400569434, doi101016jpalaeo200702037, doi101016jpalaeo200909018, doi101016jpalaeo201206024, doi101016jpalaeo201206027, doi101016s0012825200000374, doi101016s1631071303000063, doi101038ncomms1815, doi101073pnas1211526110, doi101080027246342010483632, doi101126science1116412, doi101126science1156963, doi101126science1177265, doi101126science28454232137, doi1011300091761319910190867ccapct23co2, doi1011300091761320020300123dsproe20co2, doi101139cjes20120185, doi101371journalpone0016574, doi101371journalpone0025186, doi101371journalpone0072579, doi1015259780520941434, doi10166612041, doi102475ajss32313381, horner2011dinosaur, lofgren1990reworking, openalexw2183707334, sloan1986gradual"
}

The Chicxulub asteroid impact (Mexico) and the eruption of the massive Deccan volcanic province (India) are two proposed causes of the end-Cretaceous mass extinction, which includes the demise of nonavian dinosaurs. Despite widespread acceptance of the impact hypothesis, the lack of a high-resolution eruption timeline for the Deccan basalts has prevented full assessment of their relationship to the mass extinction. Here we apply uranium-lead (U-Pb) zircon geochronology to Deccan rocks and show that the main phase of eruptions initiated ~250,000 years before the Cretaceous-Paleogene boundary and that >1.1 million cubic kilometers of basalt erupted in ~750,000 years. Our results are consistent with the hypothesis that the Deccan Traps contributed to the latest Cretaceous environmental change and biologic turnover that culminated in the marine and terrestrial mass extinctions.

@article{doi101126scienceaaa0118,
    author = "Schoene, Blair and Samperton, Kyle M. and Eddy, Michael P. and Keller, Gerta and Adatte, Thierry and Bowring, Samuel A. and Khadri, S. and Gertsch, B.",
    title = "U-Pb geochronology of the Deccan Traps and relation to the end-Cretaceous mass extinction",
    year = "2014",
    journal = "Science",
    abstract = "The Chicxulub asteroid impact (Mexico) and the eruption of the massive Deccan volcanic province (India) are two proposed causes of the end-Cretaceous mass extinction, which includes the demise of nonavian dinosaurs. Despite widespread acceptance of the impact hypothesis, the lack of a high-resolution eruption timeline for the Deccan basalts has prevented full assessment of their relationship to the mass extinction. Here we apply uranium-lead (U-Pb) zircon geochronology to Deccan rocks and show that the main phase of eruptions initiated \textasciitilde 250,000 years before the Cretaceous-Paleogene boundary and that >1.1 million cubic kilometers of basalt erupted in \textasciitilde 750,000 years. Our results are consistent with the hypothesis that the Deccan Traps contributed to the latest Cretaceous environmental change and biologic turnover that culminated in the marine and terrestrial mass extinctions.",
    url = "https://doi.org/10.1126/science.aaa0118",
    doi = "10.1126/science.aaa0118",
    openalex = "W2009674195",
    references = "doi101007s0041000203647, doi1010160009254194001404, doi1010160012821x8390211x, doi1010160016703773902135, doi101016b9780080959757003107, doi101016jchemgeo200503011, doi101016jepsl200902019, doi101016jgca201006017, doi101016s0009254197001599, doi101016s0012821x0000159x, doi101016s1631071303000063, doi1010292006gc001492, doi1010292008jb005644, doi101103physrevc41889, doi101126science1097329, doi101126science1154339, doi101126science1177265, doi101126science1215507, doi101126science1230492, doi101126science1234204, doi1011300091761319980260995adswat23co2, doi1011302014250315, doi101130b309291, doi101130g306831, doi101144gsjgs15420265"
}

The Cretaceous-Paleogene boundary marks a critical event in mammalian evolution. Using a database of 4769 mammalian specimens from the Hell Creek and lower Fort Union formations of Garfield County, northeastern Montana, I quantified temporal patterns of diversity and community structure to evaluate faunal dynamics during the last ~1.9 m.y. of the Cretaceous, the Cretaceous-Paleogene extinction and survival, and the first ~1.2 m.y. of the early Paleocene recovery and placental radiation.

@incollection{doi1011302014250315,
    author = "Wilson, Gregory P.",
    title = "Mammalian extinction, survival, and recovery dynamics across the Cretaceous-Paleogene boundary in northeastern Montana, USA",
    year = "2014",
    booktitle = "Geological Society of America eBooks",
    abstract = "The Cretaceous-Paleogene boundary marks a critical event in mammalian evolution. Using a database of 4769 mammalian specimens from the Hell Creek and lower Fort Union formations of Garfield County, northeastern Montana, I quantified temporal patterns of diversity and community structure to evaluate faunal dynamics during the last \textasciitilde 1.9 m.y. of the Cretaceous, the Cretaceous-Paleogene extinction and survival, and the first \textasciitilde 1.2 m.y. of the early Paleocene recovery and placental radiation.",
    url = "https://doi.org/10.1130/2014.2503(15)",
    doi = "10.1130/2014.2503(15)",
    openalex = "W2500553572",
    references = "archibald1982upper, doi101038nature05634, doi101046j14724642199900046x, doi101111j14610248200701094x, doi101126science1177265, doi10113000917613198210153ucbamh20co2, doi101130spe190p291, doi1016660094837320002674oaecot20co2, doi1016660094837336180, doi10166612041, doi105860choice421547, doi107312kiel11918, hotton2002palynology, openalexw1530215206, openalexw2183707334, openalexw610180004"
}

The Late Cretaceous was a time of tremendous global change, as the final stages of the Age of Dinosaurs were shaped by climate and sea level fluctuations and witness to marked paleogeographic and faunal changes, before the end-Cretaceous bolide impact. The terrestrial fossil record of Late Cretaceous Europe is becoming increasingly better understood, based largely on intensive fieldwork over the past two decades, promising new insights into latest Cretaceous faunal evolution. We review the terrestrial Late Cretaceous record from Europe and discuss its importance for understanding the paleogeography, ecology, evolution, and extinction of land-dwelling vertebrates. We review the major Late Cretaceous faunas from Austria, Hungary, France, Spain, Portugal, and Romania, as well as more fragmentary records from elsewhere in Europe. We discuss the paleogeographic background and history of assembly of these faunas, and argue that they are comprised of an endemic 'core' supplemented with various immigration waves. These faunas lived on an island archipelago, and we describe how this insular setting led to ecological peculiarities such as low diversity, a preponderance of primitive taxa, and marked changes in morphology (particularly body size dwarfing). We conclude by discussing the importance of the European record in understanding the end-Cretaceous extinction and show that there is no clear evidence that dinosaurs or other groups were undergoing long-term declines in Europe prior to the bolide impact.

@article{doi103897zookeys4698439,
    author = "Csiki‐Sava, Zoltán and Buffetaut, Éric and Ősi, Attila and Suberbiola, Xabier Pereda and Brusatte, Stephen L.",
    title = "Island life in the Cretaceous - faunal composition, biogeography, evolution, and extinction of land-living vertebrates on the Late Cretaceous European archipelago",
    year = "2015",
    journal = "ZooKeys",
    abstract = "The Late Cretaceous was a time of tremendous global change, as the final stages of the Age of Dinosaurs were shaped by climate and sea level fluctuations and witness to marked paleogeographic and faunal changes, before the end-Cretaceous bolide impact. The terrestrial fossil record of Late Cretaceous Europe is becoming increasingly better understood, based largely on intensive fieldwork over the past two decades, promising new insights into latest Cretaceous faunal evolution. We review the terrestrial Late Cretaceous record from Europe and discuss its importance for understanding the paleogeography, ecology, evolution, and extinction of land-dwelling vertebrates. We review the major Late Cretaceous faunas from Austria, Hungary, France, Spain, Portugal, and Romania, as well as more fragmentary records from elsewhere in Europe. We discuss the paleogeographic background and history of assembly of these faunas, and argue that they are comprised of an endemic 'core' supplemented with various immigration waves. These faunas lived on an island archipelago, and we describe how this insular setting led to ecological peculiarities such as low diversity, a preponderance of primitive taxa, and marked changes in morphology (particularly body size dwarfing). We conclude by discussing the importance of the European record in understanding the end-Cretaceous extinction and show that there is no clear evidence that dinosaurs or other groups were undergoing long-term declines in Europe prior to the bolide impact.",
    url = "https://doi.org/10.3897/zookeys.469.8439",
    doi = "10.3897/zookeys.469.8439",
    openalex = "W2133891947",
    references = "apesteguía2011tunasniyoj, doi101002mmng20010040112, doi101006cres20000236, doi101007s0001500812473, doi101007s0011401209171, doi101016004019518690199x, doi101016jcretres200802004, doi101016jearscirev201009005, doi101016jearscirev201203002, doi101016jgloplacha201312007, doi101016jpalaeo200412005, doi101016jpalaeo200909018, doi101016jpalaeo201206008, doi101016s0012825202000752, doi101016s1631068303000022, doi101017cbo9780511608377011, doi101017s0016756800012413, doi101017s1477201907002246, doi101038nature04633, doi101038ncomms1815, doi101038sjhdy6885841, doi101073pnas1006970107, doi101073pnas1211526110, doi101080089129632012763034, doi101080089129632013777533, doi10108010420940601006859, doi101080147720192011630927, doi101098rspb20090229, doi101111brv12128, doi101111j10963642200900617x, doi101111j10963642201000642x, doi101111j13652699200501314x, doi101111j136531211990tb00103x, doi101126science23547931156, doi1011302014250315, doi101139e72031, doi101139e93176, doi101144gsljgs1934090010405, doi101146annurevearth31100901141308, doi1012067481, doi101371journalpbio0040321, doi101371journalpone0012292, doi101371journalpone0020011, doi101371journalpone0044318, doi101371journalpone0054991, doi101371journalpone0072579, doi101371journalpone0080405, doi101525california97805202420980030015, doi10166612041, doi10167102724634200727931dtftco20co2, doi1016710390290428, doi103090610262296200073181198, doi104202app20120121, doi105860choice435902, doi105860choice514447, doi105962bhltitle59991, doi105962bhltitle68064, garilli2009first, lehman1987late, leloeuff1994the, martinsander2006bone, openalexw3015256845, openalexw51761775"
}

Whether dinosaurs were in a long-term decline or whether they were reigning strong right up to their final disappearance at the Cretaceous-Paleogene (K-Pg) mass extinction event 66 Mya has been debated for decades with no clear resolution. The dispute has continued unresolved because of a lack of statistical rigor and appropriate evolutionary framework. Here, for the first time to our knowledge, we apply a Bayesian phylogenetic approach to model the evolutionary dynamics of speciation and extinction through time in Mesozoic dinosaurs, properly taking account of previously ignored statistical violations. We find overwhelming support for a long-term decline across all dinosaurs and within all three dinosaurian subclades (Ornithischia, Sauropodomorpha, and Theropoda), where speciation rate slowed down through time and was ultimately exceeded by extinction rate tens of millions of years before the K-Pg boundary. The only exceptions to this general pattern are the morphologically specialized herbivores, the Hadrosauriformes and Ceratopsidae, which show rapid species proliferations throughout the Late Cretaceous instead. Our results highlight that, despite some heterogeneity in speciation dynamics, dinosaurs showed a marked reduction in their ability to replace extinct species with new ones, making them vulnerable to extinction and unable to respond quickly to and recover from the final catastrophic event.

@article{doi101073pnas1521478113,
    author = "Sakamoto, Manabu and Benton, Michael J. and Venditti, Chris",
    title = "Dinosaurs in decline tens of millions of years before their final extinction",
    year = "2016",
    journal = "Proceedings of the National Academy of Sciences",
    abstract = "Whether dinosaurs were in a long-term decline or whether they were reigning strong right up to their final disappearance at the Cretaceous-Paleogene (K-Pg) mass extinction event 66 Mya has been debated for decades with no clear resolution. The dispute has continued unresolved because of a lack of statistical rigor and appropriate evolutionary framework. Here, for the first time to our knowledge, we apply a Bayesian phylogenetic approach to model the evolutionary dynamics of speciation and extinction through time in Mesozoic dinosaurs, properly taking account of previously ignored statistical violations. We find overwhelming support for a long-term decline across all dinosaurs and within all three dinosaurian subclades (Ornithischia, Sauropodomorpha, and Theropoda), where speciation rate slowed down through time and was ultimately exceeded by extinction rate tens of millions of years before the K-Pg boundary. The only exceptions to this general pattern are the morphologically specialized herbivores, the Hadrosauriformes and Ceratopsidae, which show rapid species proliferations throughout the Late Cretaceous instead. Our results highlight that, despite some heterogeneity in speciation dynamics, dinosaurs showed a marked reduction in their ability to replace extinct species with new ones, making them vulnerable to extinction and unable to respond quickly to and recover from the final catastrophic event.",
    url = "https://doi.org/10.1073/pnas.1521478113",
    doi = "10.1073/pnas.1521478113",
    openalex = "W2341385457",
    references = "doi101016jcub201408034, doi101038nature11631, doi101038ncomms1815, doi101093oso97801985052350010001, doi101111brv12128, doi101111j14679868200500503x, doi101111j2041210x201100169x, doi101126science1116412, doi101126science23547931156, doi1018637jssv033i02, doi105962bhltitle59991, doi105962bhltitle82303, openalexw2097360283, sloan1986gradual"
}

In the lead-up to the Cretaceous/Paleogene mass extinction, dinosaur diversity is argued to have been either in long-term decline, or thriving until their sudden demise. The latest Cretaceous (Campanian-Maastrichtian [83-66 Ma]) of North America provides the best record to address this debate, but even here diversity reconstructions are biased by uneven sampling. Here we combine fossil occurrences with climatic and environmental modelling to quantify latest Cretaceous North American dinosaur habitat. Ecological niche modelling shows a Campanian-to-Maastrichtian habitability decrease in areas with present-day rock-outcrop. However, a continent-wide projection demonstrates habitat stability, or even a Campanian-to-Maastrichtian increase, that is not preserved. This reduction of the spatial sampling window resulted from formation of the proto-Rocky Mountains and sea-level regression. We suggest that Maastrichtian North American dinosaur diversity is therefore likely to be underestimated, with the apparent decline a product of sampling bias, and not due to a climatically-driven decrease in habitability as previously hypothesised.

@article{doi101038s41467019089972,
    author = "Chiarenza, Alfio Alessandro and Mannion, Philip D. and Lunt, Daniel J. and Farnsworth, Alex and Jones, Lewis A. and Kelland, Sarah-Jane and Allison, Peter A.",
    title = "Ecological niche modelling does not support climatically-driven dinosaur diversity decline before the Cretaceous/Paleogene mass extinction",
    year = "2019",
    journal = "Nature Communications",
    abstract = "In the lead-up to the Cretaceous/Paleogene mass extinction, dinosaur diversity is argued to have been either in long-term decline, or thriving until their sudden demise. The latest Cretaceous (Campanian-Maastrichtian [83-66 Ma]) of North America provides the best record to address this debate, but even here diversity reconstructions are biased by uneven sampling. Here we combine fossil occurrences with climatic and environmental modelling to quantify latest Cretaceous North American dinosaur habitat. Ecological niche modelling shows a Campanian-to-Maastrichtian habitability decrease in areas with present-day rock-outcrop. However, a continent-wide projection demonstrates habitat stability, or even a Campanian-to-Maastrichtian increase, that is not preserved. This reduction of the spatial sampling window resulted from formation of the proto-Rocky Mountains and sea-level regression. We suggest that Maastrichtian North American dinosaur diversity is therefore likely to be underestimated, with the apparent decline a product of sampling bias, and not due to a climatically-driven decrease in habitability as previously hypothesised.",
    url = "https://doi.org/10.1038/s41467-019-08997-2",
    doi = "10.1038/s41467-019-08997-2",
    openalex = "W2919866498",
    references = "doi101016jecolmodel201312012, doi101016jpalaeo201602033, doi101038nature15697, doi101038ncomms1815, doi101073pnas0901637106, doi101073pnas1521478113, doi10108008912969009386535, doi101111ecog03049, doi101111j13652664200601214x, doi101111j14724642201000725x, doi101111pala12329, doi101126science3287615, doi1012019781315140919, doi101371journalpone0079420, doi1018900721531, doi1023071931034, doi103897zookeys4698439, lehman1987late"
}

Titanosaurs were a globally distributed clade of Cretaceous sauropods. Historically regarded as a primarily Gondwanan radiation, there is a growing number of Eurasian taxa, with several putative titanosaurs contemporaneous with, or even pre-dating, the oldest known Southern Hemisphere remains. The early Late Cretaceous Jinhua Formation, in Zhejiang Province, China, has yielded two putative titanosaurs, Jiangshanosaurus lixianensis and Dongyangosaurus sinensis. Here, we provide a detailed re-description and diagnosis of Jiangshanosaurus, as well as new anatomical information on Dongyangosaurus. Previously, a 'derived' titanosaurian placement for Jiangshanosaurus was primarily based on the presence of procoelous anterior caudal centra. We show that this taxon had amphicoelous anterior-middle caudal centra. Its only titanosaurian synapomorphy is that the dorsal margins of the scapula and coracoid are approximately level with one another. Dongyangosaurus can clearly be differentiated from Jiangshanosaurus, and displays features that indicate a closer relationship to the titanosaur radiation. Revised scores for both taxa are incorporated into an expanded phylogenetic data matrix, comprising 124 taxa scored for 548 characters. Under equal weights parsimony, Jiangshanosaurus is recovered as a member of the non-titanosaurian East Asian somphospondylan clade Euhelopodidae, and Dongyangosaurus lies just outside of Titanosauria. However, when extended implied weighting is applied, both taxa are placed within Titanosauria. Most other 'middle' Cretaceous East Asian sauropods are probably non-titanosaurian somphospondylans, but at least Xianshanosaurus appears to belong to the titanosaur radiation. Our analyses also recover the Early Cretaceous European sauropod Normanniasaurus genceyi as a 'derived' titanosaur, clustering with Gondwanan taxa. These results provide further support for a widespread diversification of titanosaurs by at least the Early Cretaceous.

@article{doi101098rsos191057,
    author = "Mannion, Philip D. and Upchurch, Paul and Jin, Xingsheng and Zheng, Wenjie",
    title = "New information on the Cretaceous sauropod dinosaurs of Zhejiang Province, China: impact on Laurasian titanosauriform phylogeny and biogeography",
    year = "2019",
    journal = "Royal Society Open Science",
    abstract = "Titanosaurs were a globally distributed clade of Cretaceous sauropods. Historically regarded as a primarily Gondwanan radiation, there is a growing number of Eurasian taxa, with several putative titanosaurs contemporaneous with, or even pre-dating, the oldest known Southern Hemisphere remains. The early Late Cretaceous Jinhua Formation, in Zhejiang Province, China, has yielded two putative titanosaurs, Jiangshanosaurus lixianensis and Dongyangosaurus sinensis. Here, we provide a detailed re-description and diagnosis of Jiangshanosaurus, as well as new anatomical information on Dongyangosaurus. Previously, a 'derived' titanosaurian placement for Jiangshanosaurus was primarily based on the presence of procoelous anterior caudal centra. We show that this taxon had amphicoelous anterior-middle caudal centra. Its only titanosaurian synapomorphy is that the dorsal margins of the scapula and coracoid are approximately level with one another. Dongyangosaurus can clearly be differentiated from Jiangshanosaurus, and displays features that indicate a closer relationship to the titanosaur radiation. Revised scores for both taxa are incorporated into an expanded phylogenetic data matrix, comprising 124 taxa scored for 548 characters. Under equal weights parsimony, Jiangshanosaurus is recovered as a member of the non-titanosaurian East Asian somphospondylan clade Euhelopodidae, and Dongyangosaurus lies just outside of Titanosauria. However, when extended implied weighting is applied, both taxa are placed within Titanosauria. Most other 'middle' Cretaceous East Asian sauropods are probably non-titanosaurian somphospondylans, but at least Xianshanosaurus appears to belong to the titanosaur radiation. Our analyses also recover the Early Cretaceous European sauropod Normanniasaurus genceyi as a 'derived' titanosaur, clustering with Gondwanan taxa. These results provide further support for a widespread diversification of titanosaurs by at least the Early Cretaceous.",
    url = "https://doi.org/10.1098/rsos.191057",
    doi = "10.1098/rsos.191057",
    openalex = "W2970495169",
    references = "doi101016jcretres201603008, doi101016jgr201403014, doi101016jjsames201411008, doi101016jpalaeo201206008, doi101038srep34467, doi101080027246342012671204, doi101093zoolinneanzlx103, doi101093zoolinneanzly068, doi101098rspb20171219, doi101111brv12255, doi1011646zootaxa384811, doi101371journalpone0125819, doi103897zookeys4698439"
}

We report a time-calibrated stratigraphic section in Colorado that contains unusually complete fossils of mammals, reptiles, and plants and elucidates the drivers and tempo of biotic recovery during the poorly known first million years after the Cretaceous-Paleogene mass extinction (KPgE). Within ~100 thousand years (ka) post-KPgE, mammalian taxonomic richness doubled, and maximum mammalian body mass increased to near pre-KPgE levels. A threefold increase in maximum mammalian body mass and dietary niche specialization occurred at ~300 ka post-KPgE, concomitant with increased megafloral standing species richness. The appearance of additional large mammals occurred by ~700 ka post-KPgE, coincident with the first appearance of Leguminosae (the bean family). These concurrent plant and mammal originations and body-mass shifts coincide with warming intervals, suggesting that climate influenced post-KPgE biotic recovery.

@article{doi101126scienceaay2268,
    author = "Lyson, Tyler R. and Miller, Ian M. and Bercovici, Antoine and Weissenburger, Ken and Fuentes, Anthony and Clyde, William C. and Hagadorn, James W. and Butrim, Matthew J. and Johnson, Kirk R. and Fleming, Robert and Barclay, Richard S. and Maccracken, S. Augusta and Lloyd, Benjamin A. and Wilson, Gregory P. and Krause, David W. and Chester, Stephen G. B.",
    title = "Exceptional continental record of biotic recovery after the Cretaceous–Paleogene mass extinction",
    year = "2019",
    journal = "Science",
    abstract = "We report a time-calibrated stratigraphic section in Colorado that contains unusually complete fossils of mammals, reptiles, and plants and elucidates the drivers and tempo of biotic recovery during the poorly known first million years after the Cretaceous-Paleogene mass extinction (KPgE). Within \textasciitilde 100 thousand years (ka) post-KPgE, mammalian taxonomic richness doubled, and maximum mammalian body mass increased to near pre-KPgE levels. A threefold increase in maximum mammalian body mass and dietary niche specialization occurred at \textasciitilde 300 ka post-KPgE, concomitant with increased megafloral standing species richness. The appearance of additional large mammals occurred by \textasciitilde 700 ka post-KPgE, coincident with the first appearance of Leguminosae (the bean family). These concurrent plant and mammal originations and body-mass shifts coincide with warming intervals, suggesting that climate influenced post-KPgE biotic recovery.",
    url = "https://doi.org/10.1126/science.aay2268",
    doi = "10.1126/science.aay2268",
    openalex = "W2981792884",
    references = "doi101016jcub201804062, doi101038nature02403, doi101038nature09678, doi101038nature15697, doi101038nature19417, doi10107997818459358490000, doi10108010635150590947131, doi101111j14698137200902830x, doi101126science1177265, doi101126science1229237, doi101126science21545391501, doi101126scienceaau2422, doi1011302014250315, doi101186174170071060, palamarczuk2011dinoflagellate"
}

The Cretaceous/Paleogene mass extinction, 66 Ma, included the demise of non-avian dinosaurs. Intense debate has focused on the relative roles of Deccan volcanism and the Chicxulub asteroid impact as kill mechanisms for this event. Here, we combine fossil-occurrence data with paleoclimate and habitat suitability models to evaluate dinosaur habitability in the wake of various asteroid impact and Deccan volcanism scenarios. Asteroid impact models generate a prolonged cold winter that suppresses potential global dinosaur habitats. Conversely, long-term forcing from Deccan volcanism (carbon dioxide [CO 2]-induced warming) leads to increased habitat suitability. Short-term (aerosol cooling) volcanism still allows equatorial habitability. These results support the asteroid impact as the main driver of the non-avian dinosaur extinction. By contrast, induced warming from volcanism mitigated the most extreme effects of asteroid impact, potentially reducing the extinction severity.

@article{doi101073pnas2006087117,
    author = "Chiarenza, Alfio Alessandro and Farnsworth, Alexander and Mannion, Philip D. and Lunt, Daniel J. and Valdes, Paul J. and Morgan, Joanna and Allison, Peter A.",
    title = "Asteroid impact, not volcanism, caused the end-Cretaceous dinosaur extinction",
    year = "2020",
    journal = "Proceedings of the National Academy of Sciences",
    abstract = "The Cretaceous/Paleogene mass extinction, 66 Ma, included the demise of non-avian dinosaurs. Intense debate has focused on the relative roles of Deccan volcanism and the Chicxulub asteroid impact as kill mechanisms for this event. Here, we combine fossil-occurrence data with paleoclimate and habitat suitability models to evaluate dinosaur habitability in the wake of various asteroid impact and Deccan volcanism scenarios. Asteroid impact models generate a prolonged cold winter that suppresses potential global dinosaur habitats. Conversely, long-term forcing from Deccan volcanism (carbon dioxide [CO 2]-induced warming) leads to increased habitat suitability. Short-term (aerosol cooling) volcanism still allows equatorial habitability. These results support the asteroid impact as the main driver of the non-avian dinosaur extinction. By contrast, induced warming from volcanism mitigated the most extreme effects of asteroid impact, potentially reducing the extinction severity.",
    url = "https://doi.org/10.1073/pnas.2006087117",
    doi = "10.1073/pnas.2006087117",
    openalex = "W3038551147",
    references = "alvarez1980extraterrestrial, doi101007s1091400569434, doi101016jcub201804062, doi101016s0012825200000374, doi10102993jd02553, doi101038s41467019089972, doi101073pnas1211526110, doi101073pnas1319253111, doi101111brv12128, doi101111ecog03049, doi101111j14724642201000725x, doi101111j16000587200805742x, doi101126sciadvaat4858, doi101126science1177265, doi101126science1229237, doi101126science20844481095, doi101126science21545391501, doi101126scienceaau2422, doi101126scienceaay2268, doi1011302014250315, doi1011302014250502, doi101130spe247, doi101144sp35813"
}

ABSTRACT In recent models of earth-system crises, the correlation between the major Phanerozoic mass extinctions and large igneous provinces has been well established. Specifically, pulsed massive exhalations of large amounts of volcanogenic CO2 transformed Earth’s atmosphere, leading to an excessive greenhouse effect and global warming, combined with slowed oceanic circulation, oxygen deficiency, and seawater acidification. In a historical context, however, the path leading to this neocatastrophic doctrine, traced by way of ever-more-convincing proofs (in recent years, via mercury anomalies), was convoluted for many objective and notional-personal reasons. From the late eighteenth century to the revolutionary 1980s, the reception of this conceptual route in the English-language mainstream science was determined principally by the rise and fall of the orthodox nonprogressive (steady-state) paradigm of the Lyellian uniformitarian. The main cognitive steps, pioneered frequently in continental Europe, included such principal conclusions as: (1) volcanic eruptions are a natural process, consisting of heat being vented from a central incandescent core, itself a relic of an initial nebular state; (2) cataclysmic phenomena were far more intense in the geologic past, both in orogenic and nonorogenic time intervals, with a dominant nonactualistic style of fissure-type effusive activity in intraplate settings, recorded in vast trap-type basalt successions (= large igneous provinces); (3) volcanogenic gaseous emanations, dominated by carbon dioxide and water vapor, had a strong impact on the global climate in the geological past toward the global warmth mode; and (4) this “volcanic greenhouse” was deleteriously augmented by several forms of immanent stress feedback (resulting in anoxia, acidification, hypercapnia, acid rains, ultraviolet radiation, etc.). Overall, diverse global ecosystem interactions, combined with the updated large igneous province scenario, can elucidate all major destructive factors in the biosphere, such as regressive versus transgressive sea-level changes and cooling versus warming climatic responses. Notwithstanding the particularity of each major biodiversity crisis in the Phanerozoic, however, a greenhouse/icehouse volcanism-driven catastrophe is a well-confirmed key toward better understanding these biotic turnovers over a variety of time scales and feedbacks. The holistic volcanic “press-pulse” model involves the joint action of two different types of stress factors: long-lived (“press”) large igneous provinces and a variety of critically sudden (“pulse”) disturbances. Therefore, the killing effectiveness of volcanic cataclysm should be viewed not only by the large igneous province size but also by their host geology, magma plumbing system, and eruption dynamics, determining the magnitude and composition of disastrous thermogenic outgassing. In search of possible pulse signals, emphasis has recently been placed on large igneous province–related, volatile-rich, mafic-ultramafic intrusions (owing to the great fluid-bearing capacity of their magmas) and sill-type intrusions (resulting in the most-effective devolatilization of sedimentary rocks). A simultaneous burst of arc magmatism and coeval impact of arc-continent collisions (especially in tropical domain) on global weatherability are additional cumulative cataclysmic stimuli awaiting more rigorous numerical simulations.

@incollection{doi1011302020254401,
    author = "Racki, Grzegorz",
    title = "Volcanism as a prime cause of mass extinctions: Retrospectives and perspectives",
    year = "2020",
    booktitle = "Geological Society of America eBooks",
    abstract = "ABSTRACT In recent models of earth-system crises, the correlation between the major Phanerozoic mass extinctions and large igneous provinces has been well established. Specifically, pulsed massive exhalations of large amounts of volcanogenic CO2 transformed Earth’s atmosphere, leading to an excessive greenhouse effect and global warming, combined with slowed oceanic circulation, oxygen deficiency, and seawater acidification. In a historical context, however, the path leading to this neocatastrophic doctrine, traced by way of ever-more-convincing proofs (in recent years, via mercury anomalies), was convoluted for many objective and notional-personal reasons. From the late eighteenth century to the revolutionary 1980s, the reception of this conceptual route in the English-language mainstream science was determined principally by the rise and fall of the orthodox nonprogressive (steady-state) paradigm of the Lyellian uniformitarian. The main cognitive steps, pioneered frequently in continental Europe, included such principal conclusions as: (1) volcanic eruptions are a natural process, consisting of heat being vented from a central incandescent core, itself a relic of an initial nebular state; (2) cataclysmic phenomena were far more intense in the geologic past, both in orogenic and nonorogenic time intervals, with a dominant nonactualistic style of fissure-type effusive activity in intraplate settings, recorded in vast trap-type basalt successions (= large igneous provinces); (3) volcanogenic gaseous emanations, dominated by carbon dioxide and water vapor, had a strong impact on the global climate in the geological past toward the global warmth mode; and (4) this “volcanic greenhouse” was deleteriously augmented by several forms of immanent stress feedback (resulting in anoxia, acidification, hypercapnia, acid rains, ultraviolet radiation, etc.). Overall, diverse global ecosystem interactions, combined with the updated large igneous province scenario, can elucidate all major destructive factors in the biosphere, such as regressive versus transgressive sea-level changes and cooling versus warming climatic responses. Notwithstanding the particularity of each major biodiversity crisis in the Phanerozoic, however, a greenhouse/icehouse volcanism-driven catastrophe is a well-confirmed key toward better understanding these biotic turnovers over a variety of time scales and feedbacks. The holistic volcanic “press-pulse” model involves the joint action of two different types of stress factors: long-lived (“press”) large igneous provinces and a variety of critically sudden (“pulse”) disturbances. Therefore, the killing effectiveness of volcanic cataclysm should be viewed not only by the large igneous province size but also by their host geology, magma plumbing system, and eruption dynamics, determining the magnitude and composition of disastrous thermogenic outgassing. In search of possible pulse signals, emphasis has recently been placed on large igneous province–related, volatile-rich, mafic-ultramafic intrusions (owing to the great fluid-bearing capacity of their magmas) and sill-type intrusions (resulting in the most-effective devolatilization of sedimentary rocks). A simultaneous burst of arc magmatism and coeval impact of arc-continent collisions (especially in tropical domain) on global weatherability are additional cumulative cataclysmic stimuli awaiting more rigorous numerical simulations.",
    url = "https://doi.org/10.1130/2020.2544(01)",
    doi = "10.1130/2020.2544(01)",
    openalex = "W3016572426",
    references = "crossref2004perilous, doi101016s0012825200000374, doi1010292009gc002788, doi10102993rg02508, doi101029jc086ic10p09776, doi101038230042a0, doi101126science1116412, doi101126science20844481095, doi101126science2464926103, doi101144gsjgs14650749, doi1015159780295741406007, doi102475ajs2837641"
}

@incollection{crossref2021dinosaurs,
    title = "DINOSAURS AND THE CRETACEOUS-TERTIARY EXTINCTION",
    year = "2021",
    booktitle = "Disturbing the Solar System",
    url = "https://doi.org/10.2307/j.ctv1zm2tx3.18",
    doi = "10.2307/j.ctv1zm2tx3.18",
    openalex = "W4200012825",
    pages = "167-182"
}

exhibited a wulst and segmented palate, previously proposed to have arisen within extant birds. The origin of Aves is marked by larger, reshaped brains indicating selection for relatively large telencephala and eyes but not by uniquely small body size. Sensory system differences, potentially linked to these shifts, may help explain avian survivorship relative to other dinosaurs.

@article{doi101126sciadvabg7099,
    author = "Torres, Christopher R. and Norell, Mark A. and Clarke, Julia A.",
    title = "Bird neurocranial and body mass evolution across the end-Cretaceous mass extinction: The avian brain shape left other dinosaurs behind",
    year = "2021",
    journal = "Science Advances",
    abstract = "exhibited a wulst and segmented palate, previously proposed to have arisen within extant birds. The origin of Aves is marked by larger, reshaped brains indicating selection for relatively large telencephala and eyes but not by uniquely small body size. Sensory system differences, potentially linked to these shifts, may help explain avian survivorship relative to other dinosaurs.",
    url = "https://doi.org/10.1126/sciadv.abg7099",
    doi = "10.1126/sciadv.abg7099",
    openalex = "W3186419283",
    references = "doi101016jcub201804062, doi101098rsos170975, doi101111j155856461951tb02756x, doi101371journalpone0082000, doi10166613052"
}

The earliest phases of mammalian recovery following the Cretaceous–Paleogene (K–Pg) mass extinction are incompletely known but crucial to understanding the development of modern terrestrial ecosystems. Here we report new mammalian faunal data from three vertebrate microfossil assemblages in the Hell Creek region of northeastern Montana, the deposition of which we constrain to within the first 28–80 ka of the Paleocene using new stratigraphic observations within a high-resolution chronostratigraphic framework. We quantified the taxonomic diversity among these three assemblages and five other assemblages from both the Hell Creek region and Denver Basin, together spanning the first ca. 300 ka post-K–Pg mass extinction. Our results allowed us to sub-divide the established ‘disaster’ and ‘recovery’ phases of recovery into the following sub-phases: (i) early disaster, characterized by the presence of ‘dead clades walking,’ high relative abundance of bloom taxa, and the appearance of post-mass-extinction immigrants, (ii) late disaster, characterized by a reduction in the number of ‘dead clades walking,’ continued high relative abundance of bloom taxa, and a more diverse assemblage of immigrants, (iii) early recovery, characterized by decreased relative abundance of bloom taxa, and continued immigration, and (iv) late recovery, characterized by the onset of in situ diversification. We note important differences in the pattern and timing of mammalian faunal succession between the Hell Creek and Denver Basin, suggesting that post-K–Pg mammalian recovery was spatially heterogeneous. Our results provided a new model for post-K–Pg mammalian biotic recovery that can now be tested with other earliest Paleocene assemblages across western North America.

@article{doi1010800272463420232222777,
    author = "Claytor, Jordan R. and Weaver, Lucas N. and Tobin, Thomas and Wilson, Gregory P.",
    title = "New mammalian local faunas from the first ca. 80 ka of the Paleocene in northeastern Montana and a revised model of biotic recovery from the Cretaceous–Paleogene mass extinction",
    year = "2022",
    journal = "Journal of Vertebrate Paleontology",
    abstract = "The earliest phases of mammalian recovery following the Cretaceous–Paleogene (K–Pg) mass extinction are incompletely known but crucial to understanding the development of modern terrestrial ecosystems. Here we report new mammalian faunal data from three vertebrate microfossil assemblages in the Hell Creek region of northeastern Montana, the deposition of which we constrain to within the first 28–80 ka of the Paleocene using new stratigraphic observations within a high-resolution chronostratigraphic framework. We quantified the taxonomic diversity among these three assemblages and five other assemblages from both the Hell Creek region and Denver Basin, together spanning the first ca. 300 ka post-K–Pg mass extinction. Our results allowed us to sub-divide the established ‘disaster’ and ‘recovery’ phases of recovery into the following sub-phases: (i) early disaster, characterized by the presence of ‘dead clades walking,’ high relative abundance of bloom taxa, and the appearance of post-mass-extinction immigrants, (ii) late disaster, characterized by a reduction in the number of ‘dead clades walking,’ continued high relative abundance of bloom taxa, and a more diverse assemblage of immigrants, (iii) early recovery, characterized by decreased relative abundance of bloom taxa, and continued immigration, and (iv) late recovery, characterized by the onset of in situ diversification. We note important differences in the pattern and timing of mammalian faunal succession between the Hell Creek and Denver Basin, suggesting that post-K–Pg mammalian recovery was spatially heterogeneous. Our results provided a new model for post-K–Pg mammalian biotic recovery that can now be tested with other earliest Paleocene assemblages across western North America.",
    url = "https://doi.org/10.1080/02724634.2023.2222777",
    doi = "10.1080/02724634.2023.2222777",
    openalex = "W4385200530",
    references = "alvarez1980extraterrestrial, alvarez1981extraterrestrial, doi10100797814899304533, doi1010160022519366900130, doi101016s0037073887800064, doi101038163688a0, doi101093comjnl94373, doi101126science1230492, doi1023071934145, doi10298916085910409503825"
}

Continental Cretaceous-Paleogene boundary sections are best known from North America, where they invariably exhibit a marked shift in sedimentary facies at or very near the boundary level. Uppermost Cretaceous strata typically reflect water-logged soils and unstable meandering-river deposits, whereas lowermost Paleogene strata typically reflect coal swamps and broad, stable meander-belt deposits. Causal links between facies shifts at the Cretaceous-Paleogene boundary and the end-Cretaceous mass extinction have been largely dismissed. Here, we present five new Cretaceous-Paleogene boundary sections identified via iridium anomalies in the Bighorn and Williston basins and assess the sedimentological changes that occur at North American Cretaceous-Paleogene boundaries. We hypothesize that the geographically widespread Cretaceous–Paleogene facies shifts were driven by the extinction of dinosaur megafauna. Large-bodied dinosaurs likely promoted open vegetation structure, prompting fluvial avulsion and clastic sediment input to distal floodplains. After the end-Cretaceous mass extinction, dense forests could establish, stabilizing meander belts and starving the floodplain of clastic sediment, favoring the accumulation of organic-rich strata. More empirical data are needed, but facies change in continental Cretaceous-Paleogene boundary sections suggests dinosaurs were ecosystem engineers that promoted habitat openness in the Late Cretaceous, and their extinction likely led to a dramatic reorganization of ecosystem structure in the earliest Paleogene. Dinosaurs promoted open habitats in the Late Cretaceous, and their extinction could have led to a radical reorganization of the landscape and ecosystem structure at the beginning of the Paleogene, according to sedimentology, biostratigraphy, and geochemistry data from western North America.

@article{doi101038s43247025026738,
    author = "Weaver, Lucas N. and Tobin, Thomas and Sprain, Courtney J. and Wilson, Paige and Korasidis, Vera A. and Carvalho, Mónica R. and Kaskes, Pim and Fendley, Isabel",
    title = "Dinosaur extinction can explain continental facies shifts at the Cretaceous-Paleogene boundary",
    year = "2025",
    journal = "Communications Earth \& Environment",
    abstract = "Continental Cretaceous-Paleogene boundary sections are best known from North America, where they invariably exhibit a marked shift in sedimentary facies at or very near the boundary level. Uppermost Cretaceous strata typically reflect water-logged soils and unstable meandering-river deposits, whereas lowermost Paleogene strata typically reflect coal swamps and broad, stable meander-belt deposits. Causal links between facies shifts at the Cretaceous-Paleogene boundary and the end-Cretaceous mass extinction have been largely dismissed. Here, we present five new Cretaceous-Paleogene boundary sections identified via iridium anomalies in the Bighorn and Williston basins and assess the sedimentological changes that occur at North American Cretaceous-Paleogene boundaries. We hypothesize that the geographically widespread Cretaceous–Paleogene facies shifts were driven by the extinction of dinosaur megafauna. Large-bodied dinosaurs likely promoted open vegetation structure, prompting fluvial avulsion and clastic sediment input to distal floodplains. After the end-Cretaceous mass extinction, dense forests could establish, stabilizing meander belts and starving the floodplain of clastic sediment, favoring the accumulation of organic-rich strata. More empirical data are needed, but facies change in continental Cretaceous-Paleogene boundary sections suggests dinosaurs were ecosystem engineers that promoted habitat openness in the Late Cretaceous, and their extinction likely led to a dramatic reorganization of ecosystem structure in the earliest Paleogene. Dinosaurs promoted open habitats in the Late Cretaceous, and their extinction could have led to a radical reorganization of the landscape and ecosystem structure at the beginning of the Paleogene, according to sedimentology, biostratigraphy, and geochemistry data from western North America.",
    url = "https://doi.org/10.1038/s43247-025-02673-8",
    doi = "10.1038/s43247-025-02673-8",
    openalex = "W4414183294",
    references = "doi101016jearscirev2023104630, doi1010800272463420232222777"
}