Origin of Cretaceous-Palaeogene impactor + geological revolutions in late 20th and early 21st centuries (free pdfs)
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Ben Creisler
Jul 17, 2026, 2:34:40 PM (6 days ago) Jul 17
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Ben Creisler
Georgy V. Makhatadze, Frédéric Moynier, Leslie-Anne Brun, Steven Goderis, Philippe Claeys & Christian Koeberl (2026)
The origin of Cretaceous-Palaeogene impactor revealed by nickel isotopes
Science Advances 12(29): eaef4858
DOI: 10.1126/sciadv.aef4858
https://www.science.org/doi/10.1126/sciadv.aef4858
Free pdf:
https://www.science.org/doi/epdf/10.1126/sciadv.aef4858
Sixty-six million years ago, non-avian dinosaurs and other taxa went extinct during one of the largest mass extinctions in the history of life on Earth. The extinction was likely caused by an asteroid of unknown origin, responsible for the Chicxulub impact structure. Existing evidence identifies the impactor as an asteroid, similar to carbonaceous chondrites. However, carbonaceous chondrites are a diverse class of meteorites, leaving the exact nature of the impactor unclear. By measuring Ni isotopes in marine clays containing the impact ejecta, we constrain the impactor to one group of carbonaceous chondrites—CO chondrites—and some ungrouped chondrites. This study highlights the use of Ni isotopes in fingerprinting extraterrestrial materials on Earth. Given that CO chondrites are “dry” compared to the other carbonaceous chondrites and would have delivered much less volatiles, which are thought to be essential in causing the extinction, this work allows further studies of the mechanism behind the extinction.
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News:
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Douglas H. Erwin (2026)
Geological Revolutions in the Late 20th and Early 21st Centuries: Plate Tectonics, Extraterrestrial Impacts, and Snowball Earth
Natural Sciences 6(3): e70079
doi: https://doi.org/10.1002/ntls.70079
https://onlinelibrary.wiley.com/doi/10.1002/ntls.70079
Free pdf:
https://onlinelibrary.wiley.com/doi/epdf/10.1002/ntls.70079
During the late 20th and early 21st century three conceptual revolutions reordered our understanding of the history of the Earth: The spread of plate tectonic theory from the 1960s onward which brought geology the first meaningful theory for building mountains and the migration of continents; the rebirth of catastrophism in 1980 with the discovery of an iridium spike coincident with the end-Cretaceous mass extinction; and recognition of two extraordinary glaciations extending to the equator, known as Snowball Earths, between 717 and 635 million years ago. Each of these challenged long-held views of geologists and represents intellectual revolutions in our understanding of the dynamics and history of the Earth. Each episode also provided new conceptual apparatuses with pervasive and far-reaching implications for many aspects of geology. Yet these three episodes differ in the scale of the conceptual changes required of geologists and the extent to which they triggered a reformulation of geological thinking. Moreover, whether these events represent canonical Kuhnian scientific revolutions is uncertain. Numerous historians of geology have discussed plate tectonics in the context of Kuhn's views of scientific revolutions, and some have discussed impact theory, but the Snowball Earth hypothesis has been less widely evaluated. Here I conclude that these episodes require broadening our understanding of conceptual change in the sciences to recognize events at a variety of scales, and that contra Kuhn, some of these changes may represent genuine progress.
Key Points
Three major conceptual advances occurred in late 20th century Earth sciences; plate tectonics; an impact theory for the end-Cretaceous mass extinction; and the Snowball Earth hypothesis for late Neoproterozoic glaciations.
These examples differ in scale and thus in the extent to which they generated a reorganization of geological thinking.
These episodes do not match Kuhn's theory of paradigm shifts but instead suggest that Earth sciences advance by conceptual advances of varying magnitude.
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Recent geology papers:
Free pdf:
Georgy V. Makhatadze, Frédéric Moynier, Leslie-Anne Brun, Steven Goderis, Philippe Claeys & Christian Koeberl (2026)
The origin of Cretaceous-Palaeogene impactor revealed by nickel isotopes
Science Advances 12(29): eaef4858
DOI: 10.1126/sciadv.aef4858
https://www.science.org/doi/10.1126/sciadv.aef4858
Free pdf:
https://www.science.org/doi/epdf/10.1126/sciadv.aef4858
Sixty-six million years ago, non-avian dinosaurs and other taxa went extinct during one of the largest mass extinctions in the history of life on Earth. The extinction was likely caused by an asteroid of unknown origin, responsible for the Chicxulub impact structure. Existing evidence identifies the impactor as an asteroid, similar to carbonaceous chondrites. However, carbonaceous chondrites are a diverse class of meteorites, leaving the exact nature of the impactor unclear. By measuring Ni isotopes in marine clays containing the impact ejecta, we constrain the impactor to one group of carbonaceous chondrites—CO chondrites—and some ungrouped chondrites. This study highlights the use of Ni isotopes in fingerprinting extraterrestrial materials on Earth. Given that CO chondrites are “dry” compared to the other carbonaceous chondrites and would have delivered much less volatiles, which are thought to be essential in causing the extinction, this work allows further studies of the mechanism behind the extinction.
****
News:
=====
Free pdf:
Douglas H. Erwin (2026)
Geological Revolutions in the Late 20th and Early 21st Centuries: Plate Tectonics, Extraterrestrial Impacts, and Snowball Earth
Natural Sciences 6(3): e70079
doi: https://doi.org/10.1002/ntls.70079
https://onlinelibrary.wiley.com/doi/10.1002/ntls.70079
Free pdf:
https://onlinelibrary.wiley.com/doi/epdf/10.1002/ntls.70079
During the late 20th and early 21st century three conceptual revolutions reordered our understanding of the history of the Earth: The spread of plate tectonic theory from the 1960s onward which brought geology the first meaningful theory for building mountains and the migration of continents; the rebirth of catastrophism in 1980 with the discovery of an iridium spike coincident with the end-Cretaceous mass extinction; and recognition of two extraordinary glaciations extending to the equator, known as Snowball Earths, between 717 and 635 million years ago. Each of these challenged long-held views of geologists and represents intellectual revolutions in our understanding of the dynamics and history of the Earth. Each episode also provided new conceptual apparatuses with pervasive and far-reaching implications for many aspects of geology. Yet these three episodes differ in the scale of the conceptual changes required of geologists and the extent to which they triggered a reformulation of geological thinking. Moreover, whether these events represent canonical Kuhnian scientific revolutions is uncertain. Numerous historians of geology have discussed plate tectonics in the context of Kuhn's views of scientific revolutions, and some have discussed impact theory, but the Snowball Earth hypothesis has been less widely evaluated. Here I conclude that these episodes require broadening our understanding of conceptual change in the sciences to recognize events at a variety of scales, and that contra Kuhn, some of these changes may represent genuine progress.
Key Points
Three major conceptual advances occurred in late 20th century Earth sciences; plate tectonics; an impact theory for the end-Cretaceous mass extinction; and the Snowball Earth hypothesis for late Neoproterozoic glaciations.
These examples differ in scale and thus in the extent to which they generated a reorganization of geological thinking.
These episodes do not match Kuhn's theory of paradigm shifts but instead suggest that Earth sciences advance by conceptual advances of varying magnitude.
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