Timeline of Cretaceous–Paleogene extinction event research

Artist's depiction of the end-Cretaceous impact event

Since the 19th century, a significant amount of research has been conducted on the Cretaceous–Paleogene extinction event, the mass extinction that ended the dinosaur-dominated Mesozoic Era and set the stage for the Age of Mammals, or Cenozoic Era. A chronology of this research is presented here.

Paleontologists have recognized that a significant transition occurred between the Mesozoic and Cenozoic eras at least since the 1820s.[1] Around this time dinosaur fossils were first being described in the scientific literature. Nevertheless, so few dinosaurs were known that the significance of their passing went unrecognized and little scientific effort was exerted toward finding an explanation.[2] As more and more different kinds of dinosaurs were discovered, their extinction and replacement by mammals was recognized as significant but dismissed with little examination as a natural consequence of the mammals' supposed innate superiority.[3] Consequently, paleontologist Michael J. Benton has called the years up to 1920 as the "Nonquestion Phase" of Cretaceous–Paleogene extinction research.[4]

Ideas that evolution might proceed along pre-ordained patterns or that evolutionary lineages might age, deteriorate, and die like individual animals became popular starting in the late 19th century, but were superseded by the Neo-Darwinian synthesis.[5] The aftermath of this transition brought renewed interest to the extinction at the end of the Cretaceous.[6] Paleontologists began dabbling in the subject, proposing environmental changes during the Cretaceous like mountain-building, dropping temperatures or volcanic eruptions as explanation for the extinction of the dinosaurs.[7] Nevertheless, much of the research occurring during this period lacked rigor, evidential support or depended on tenuous assumptions.[8] Michael J. Benton called the years between 1920 and 1970 the "Dilettante Phase" of Cretaceous–Paleogene extinction research.[4]

In 1970, paleontologists began studying the Cretaceous–Paleogene extinction in a detailed, rigorous way.[9] Benton considered this to be the beginning of the "Professional Phase" of Cretaceous–Paleogene extinction research. Early in this phase, the pace of the extinctions and the potential role of the Deccan Traps volcanism in India were major subjects of interest.[10] In 1980, father and son duo Luis and Walter Alvarez reported anomalously high levels of the platinum group metal iridium from the K–Pg boundary, but because iridium is rare in Earth's crust they argued that an asteroid impact was needed to account for it. This suggestion set off a bitter controversy. Evidence for an impact continued to mount, like the discovery of shocked quartz at the K–Pg boundary. In 1991, Alan Hildebrand and William Boynton reported the Chicxulub crater in the Yucatan peninsula of Mexico as a probable impact site. While the controversy continued, the accumulating evidence gradually began to sway the scientific community toward the Alvarez hypothesis. In 2010, an international panel of researchers concluded that impact best explained the extinction event and that Chicxulub was indeed the resulting crater.[11]


Because the estimated date of the object's impact and the Cretaceous–Paleogene boundary (K–Pg boundary) coincide, there is now a scientific consensus that this impact was the Cretaceous–Paleogene extinction event which caused the death of most of the planet's non-avian dinosaurs and many other species.[12][13] The impactor's crater is just over 177 kilometers in diameter,[14] making it the third largest known impact crater on Earth.

19th century

Portrait of Georges Cuvier, who recognized the vast difference in the faunas of the Mesozoic and Cenozoic eras

1820s

1825

1830s

1831

1840s

1842

1850s

Othniel Charles Marsh interpreted the extinction of the dinosaurs as a gradual process

1854

1880s

1882

1890s

1898

20th century

An early 20th century restoration of Stegosaurus by Charles R. Knight

1900s

1905

1910s

The enlarged pituitary of a human with acromegaly

1910

1917

1920s

1921

Deforming arthrides in dinosaur vertebrae

1922

1923

1925

1928

1929

1930s

1939

1940s

1942

1945

1946

1949

1950s

1950s

1954

1956

1960s

A swarm of caterpillars denuding a plant of vegetation

1960s

1962

1967

1968

1970s

1970s

1970

1971

A map showing the location of the large igneous provinces of the world. The Deccan Traps are represented by the purple region in India

1972

1973

1974

1976

A panorama of Gubbio, Italy

1977

Volcanism was once popularly hypothesized to have been a causative factor in the Cretaceous–Paleogene mass extinction

1978

Fragments of iridium

1979

1980s

1980

1981

1982

A Brazilian foraminiferan microfossil dating to shortly after the end of the Cretaceous
A sample of the iridium-rich Cretaceous–Tertiary boundary from Wyoming

1983

The Snowbird Ski Resort, site of the contentious Cretaceous–Paleogene extinction event conferences

1984

A modern wildfire

1985

A sedimentary rock showing signs of bioturbation

1986

The resonance structures of nitric acid

1987

1988

Patterns of temperature-dependent sex-determination in reptiles

1989

1990s

The gravitational anomalies signaling the presence of the Chicxulub Crater

1990

Location of the Chicxulub Crater on the Yucatan Peninsula of Mexico

1991

Chemical structure of sulfuric acid

1992

Map of New Zealand

1993

The Western Interior Seaway of North America at its greatest extent, c. 75 million years ago

1994

1995

1996

A fossil Inoceramus shell
Sea level over time during the Phanerozoic eon

1997

Artistic restorations of various members of the end-Cretaceous Hell Creek paleofauna

1998

1999

21st century

2000s

A modern member of the shark genus Chiloscyllium, which survived the Cretaceous–Paleogene extinction event

2000

2001

2002

2010s

2010

See also

Footnotes

  1. 1 2 3 Benton (1990); "Early 19th Century Views of Extinction", page 373.
  2. Benton (1990); "Early 19th Century Views of Extinction", page 372.
  3. 1 2 Benton (1990); "Post-Darwinian Interpretations", page 376.
  4. 1 2 Benton (1990); "Introduction", page 371.
  5. For information on orthogenesis and its role in the history of Cretaceous–Paleogene extinction event research, see Benton (1990); "Post-Darwinian Interpretations", page 376. For the impact of the rise of neodarwinism, see Benton (1990); "Racial Senility", page 379.
  6. 1 2 Benton (1990); "Racial Senility", page 379.
  7. 1 2 3 4 5 6 7 8 Benton (1990); "Biotic and Physical Factors", page 380.
  8. Benton (1990); "Problems with the 'Dilettante' Approach", pages 385–386.
  9. Benton (1990); "Background", pages 386–387.
  10. For the relevance of the pace of the extinction to early "Professional Phase" Cretaceous–Paleogene extinction research, see Benton (1990); "Introduction", page 371. For the proposal of the Deccan Traps as a putative extinction mechanism, see Powell (1998); "The Volcanic Rival", page 85.
  11. 1 2 Schulte et al. (2010); in passim.
  12. "International Consensus — Link Between Asteroid Impact and Mass Extinction Is Rock Solid". www.lpi.usra.edu. Retrieved 2015-10-28.
  13. Schulte, Peter (March 5, 2010). "The Chicxulub Asteroid Impact and Mass Extinction at the Cretaceous-Paleogene Boundary" (PDF). Science. 327: 1214–8. Bibcode:2010Sci...327.1214S. PMID 20203042. doi:10.1126/science.1177265. Archived from the original (PDF) on June 25, 2015. Retrieved 2015-06-25.
  14. http://www.bbc.com/news/science-environment-39922998
  15. Benton (1990); "The Dinosauria", page 375.
  16. Powell (1998); "Return of the Pterodactyl", page 127.
  17. Benton (1990); "Post-Darwinian Interpretations", pages 376–377.
  18. 1 2 For Woodward's speech, see Benton (1990); "Racial Senility", page 379. For a definition and discussion of racial senility, see "Post-Darwinian Interpretations", page 376.
  19. 1 2 3 4 5 Benton (1990); "I. Biotic causes", page 382.
  20. Carpenter (1999); "Reason 6. Killer Dinosaurs", page 257.
  21. 1 2 3 4 5 6 7 8 9 Benton (1990); "II. Abiotic (physical) causes", page 384.
  22. Benton (1990); "Biotic and Physical Factors", pages 380–381.
  23. 1 2 3 4 5 6 7 Benton (1990); "II. Abiotic (physical) causes", page 383.
  24. 1 2 3 4 5 6 Powell (1998); "The Red Devil", page 103.
  25. 1 2 3 4 5 Benton (1990); "II. Abiotic (physical) causes", page 385.
  26. 1 2 Powell (1998); "The Volcanic Rival", page 85.
  27. Powell (1998); "Stones from the Sky", page 36.
  28. 1 2 Powell (1998); "Losing by a Nose", page 19.
  29. Benton (1990); "I. Biotic causes", page 383.
  30. Powell (1998); "The Son in Italy", page 10.
  31. Carpenter (1999); "Reason 4. Carbon Dioxide/Oxygen Imbalance", page 255.
  32. Carpenter (1999); "Reason 4. Carbon Dioxide/Oxygen Imbalance", pages 255–256.
  33. Carpenter (1999); "Reason 3. Eggshell Too Thin, Eggshell Too Thick", pages 253–254.
  34. Carpenter (1999); "Reason 3. Eggshell Too Thin, Eggshell Too Thick", page 254.
  35. Carpenter (1999); "Reason 3. Eggshell Too Thin, Eggshell Too Thick", pages 254–255.
  36. Powell (1998); "The Greatest Mystery", page xvi.
  37. 1 2 3 4 Powell (1998); "Losing by a Nose", page 20.
  38. 1 2 3 4 5 6 7 Archibald and Fastovsky (2004); "Asteroid Impact", page 674.
  39. Powell (1998); "Iridium", page 16.
  40. 1 2 3 4 Archibald and Fastovsky (2004); "The Plant Record", page 682.
  41. Powell (1998); "Prediction 1: Impact effects will be seen worldwide at the K-T boundary.", page 58.
  42. 1 2 Powell (1998); "Plants", page 150.
  43. Carpenter (1999); "Reason 3. Eggshell Too Thin, Eggshell Too Thick", page 255.
  44. 1 2 3 Powell (1998); "Alvarez Predictions", page 57.
  45. 1 2 3 Powell (1998); "Prediction 1: Impact effects will be seen worldwide at the K-T boundary.", page 57.
  46. 1 2 Powell (1998); "Prediction 7: Unanticipated discoveries will be made.", page 63.
  47. 1 2 3 Powell (1998); "Iridium Hills", page 75.
  48. 1 2 3 4 Powell (1998); "Mysterious Spherules", page 82.
  49. 1 2 Powell (1998); "The Red Devil", pages 102–103.
  50. Powell (1998); "Ammonites", page 146.
  51. Powell (1998); "Plants", page 149.
  52. 1 2 3 Archibald and Fastovsky (2004); "Tempo of Vertebrate Turnover at the K/T Boundary", page 679.
  53. Powell (1998); "Sampling Effects", page 135.
  54. Powell (1998); "Sampling Effects", pages 135–136.
  55. 1 2 3 4 5 6 Archibald and Fastovsky (2004); "Corollaries of Asteroid Impact", page 681.
  56. 1 2 3 4 5 6 7 Archibald and Fastovsky (2004); "The Marine Record", page 682.
  57. Powell (1998); "Sampling Effects", page 136.
  58. Powell (1998); "The Death of the Dinosaurs", page 160.
  59. 1 2 Powell (1998); "Acrimony", page 162.
  60. 1 2 Powell (1998); "Acrimony", page 160.
  61. 1 2 Powell (1998); "Foraminifera", page 152.
  62. 1 2 3 4 Archibald and Fastovsky (2004); "Corollaries of Asteroid Impact", page 680.
  63. 1 2 Powell (1998); "Counterattack", page 67.
  64. Powell (1998); "Preemptive Strike", page 71.
  65. Powell (1998); "Are All Mass Extinctions Caused by Collision?", page 183.
  66. Powell (1998); "Prediction 5: The K-T boundary clays will contain shock metamorphic effects.", page 60.
  67. Powell (1998); "Prediction 5: The K-T boundary clays will contain shock metamorphic effects.", pages 60–61.
  68. Powell (1998); "Preemptive Strike", pages 71–74.
  69. Powell (1998); "Preemptive Strike", page 72.
  70. Powell (1998); "Preemptive Strike", page 73.
  71. 1 2 Powell (1998); "Career Damage", page 94.
  72. Powell (1998); "Clues", page 98.
  73. Powell (1998); "Acrimony", pages 162–163.
  74. Powell (1998); "To Hell Creek and Back", page 171.
  75. Powell (1998); "Prediction 7: Unanticipated discoveries will be made.", pages 62–63.
  76. Powell (1998); "Iridium Hills", pages 75–76.
  77. Powell (1998); "Shocked Minerals", pages 78–79.
  78. 1 2 3 4 Powell (1998); "Volcanic Iridium", page 86.
  79. Powell (1998); "Iridium Hills", page 76.
  80. 1 2 3 Powell (1998); "Shocked Minerals", page 80.
  81. 1 2 3 4 Powell (1998); "Ejecta Deposits", page 111.
  82. Powell (1998); "Prediction 2: Elsewhere in the geologic column, iridium and other markers of impact will be uncommon.", pages 58–59.
  83. Powell (1998); "Foraminifera", page 155.
  84. Powell (1998); "Topography", pages 106–107.
  85. 1 2 3 Powell (1998); "Topography", page 107.
  86. Powell (1998); "Acrimony", page 165.
  87. Powell (1998); "Ammonites", page 147.
  88. 1 2 Powell (1998); "Foraminifera", pages 152–153.
  89. Carpenter (1999); "Reason 1. Too Many Males— Too Many Females", page 248.
  90. Powell (1998); "Prediction 3: Iridium anomalies will be associated with proven meteorite impact craters.", page 59.
  91. 1 2 Powell (1998); "The Red Devil", page 102.
  92. Archibald and Fastovsky (2004); "Volcanism", page 673.
  93. 1 2 Archibald and Fastovsky (2004); "Dinosaur Diversity during the Last Ten Million Years of the Cretaceous", page 677.
  94. Powell (1998); "An Exercise in Newspeak", page 34.
  95. Powell (1998); "Iridium Hills", page 77.
  96. Powell (1998); "Sampling Effects", page 138.
  97. Powell (1998); "Triumph of the Volunteers", pages 173–174.
  98. Powell (1998); "Prediction 7: Unanticipated discoveries will be made.", page 64.
  99. 1 2 Powell (1998); "Age", page 109.
  100. 1 2 Archibald and Fastovsky (2004); "Geologic Events at or Near the K/T Boundary", page 672.
  101. 1 2 Archibald and Fastovsky (2004); "Global Marine Regression", page 673.
  102. 1 2 Powell (1998); "Survival Across the K-T Boundary at Hell Creek", page 172.
  103. Archibald and Fastovsky (2004); "Pattern of Vertebrate Turnover at the K/T Boundary", page 679.
  104. Powell (1998); "Career Damage", page 93.
  105. Powell (1998); "Career Damage", pages 93–94.
  106. Powell (1998); "Manson", page 100.
  107. Powell (1998); "Geochemistry", page 110.
  108. 1 2 Powell (1998); "Ejecta Deposits", page 112.
  109. Powell (1998); "The Zircon Fingerprint", page 118.
  110. Powell (1998); "The Zircon Fingerprint", page 119.
  111. Powell (1998); "The Zircon Fingerprint", pages 116–119.
  112. Powell (1998); "Ejecta Deposits", pages 112–113.
  113. Powell (1998); "Prediction 7: Unanticipated discoveries will be made.", pages 63–64.
  114. Powell (1998); "Indian Iridium", pages 91–92.
  115. Powell (1998); "Indian Iridium", page 92.
  116. Powell (1998); "Theories of Dinosaur Extinction", page 168.
  117. Archibald and Fastovsky (2004); "Corollaries of Marine Regression", pages 679–680.
  118. Archibald and Fastovsky (2004); "The Marine Record", page 682. See also Powell (1998); "Ammonites", page 148.
  119. Powell (1998); "Iridium Hills", page 78.
  120. Powell (1998); "Volcanic Iridium", pages 86–87.
  121. Powell (1998); "Size and Shape", pages 105–106.
  122. Powell (1998); "Size and Shape", page 106.
  123. Powell (1998); "Predictions Met", page 113.
  124. Powell (1998); "Foraminifera", pages 154–155.
  125. Archibald and Fastovsky (2004); "Corollaries of Marine Regression", page 680.
  126. Powell (1998); "Foraminifera", page 154.
  127. Archibald and Fastovsky (2004); "Multiple Causes for the K/T Extinctions", page 683.
  128. Powell (1998); "Hell on Earth", page 178.
  129. Lockley and Meyer (2000); "The Last European Dinosaurs," page 239.
  130. Archibald and Fastovsky (2004); "Pattern of Vertebrate Turnover at the K/T Boundary", page 677.
  131. 1 2 Archibald and Fastovsky (2004); "A Single Cause for the K/T Extinctions", page 684.

References

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