page_title: Timeline of Cretaceous–Paleogene extinction event research
section_title: 1970s
hierarchical_section_title: Timeline of Cretaceous–Paleogene extinction event research / 20th century / 1970s
caption_attribution_description: English: extinction of dinosaurs in Deccan Traps in Western Ghats, India. See also en:Talk:Deccan Traps#Image: artist's rendition of dinosaur extinction.
context_page_description: 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. 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. 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. Consequently, paleontologist Michael J. Benton has called the years up to 1920 as the "Nonquestion Phase" of Cretaceous–Paleogene extinction research.
context_section_description: 1970s
  PEMEX continued looking for oil deposits associated with a large circular structure in the Yucatan Peninsula.
  1970
  C. B. Hatfield and M. J. Camp suggested that the dinosaurs went extinct due to Earth's "[o]scillations about the galactic plane".
  1971
  D. A. Russel and Tucker proposed that a nearby supernova emitted a burst of electromagnetic radiations and cosmic rays that killed off the dinosaurs.
  1972
  Peter Vogt reported evidence of intense volcanic activity occurring in India around the end of the Cretaceous. He hypothesized that this volcanic activity released poisonous trace elements which brought about the mass extinction.
  1973
  Harold Urey argued that comet impacts may have caused mass extinctions in the past and may have been responsible for demarcating the periods of the geologic time scale.
  1974
  Jan Smit began studying the extinction of foraminifera at the K–T boundary in Caravaca, Spain. He observed that some of these extinctions must have been rapid.
  1976
  T. Swain proposed that when flowering plants evolved their tissues contained alkaloids and tannins that poisoned the dinosaurs, leading to their extinction.
  1977
  Alvarez and others published their research on the magnetic reversals of the Cretaceous–Tertiary boundary interval recorded in the rocks at Gubbio, Italy. They proposed that these rocks be regarded as the standard to which other rocks thought to be of this age are compared.
  Spring: Jan Smit sent 100 rock samples from the K–T boundary at Caravaca to a laboratory in Delft for compositional analysis. The results uncovered high levels of metals like antimony, chromium, cobalt, nickel, and selenium. These unusual findings led Smit to suspect that the mass extinction at the end of the Cretaceous may have had an extraterrestrial cause.
  Robert T. Bakker argued that Earth's terrain flattened out during the Late Cretaceous, reducing the area of the dinosaurs' preferred habitats and helping to drive them to extinction.
  1978
  B. W. Oelofsen argued that kimberlite volcanoes were very common during the Late Cretaceous and emitted large quantities of carbon dioxide into the atmosphere. The coincidental drop in sea level at this time period led to a drop in the population of phytoplankton that would have otherwise ingested the excess CO
  2. The unchecked CO
  2 levels would make it difficult for warm-blooded dinosaur eggs buried in nests to obtain enough oxygen through passive gas exchange with the atmosphere and the embryos would suffocate. By contrast cold blooded animals would have lower oxygen demands and may have been able to endure these conditions, explaining the survival of other egg-laying reptile groups.
  Dewey McLean argued that volcanic CO
  2 emissions during the Cretaceous led to a greenhouse effect that altered earth's climate and ocean currents, leading to the extinction at the end of the period.
  Penfield and Camargo detected a giant sub-surface crater in the Yucatan Peninsula because of its unusual magnetic and gravitational signature.
  Cloudsley-Thompson suggested that if dinosaurs were warm-blooded, increasing temperatures could have caused them to overheat and driven them extinct.
  1979
  H. K. Erben and others reported that eggs attributed to Hypselosaurus exhibit increasing rates of paleopathology like overly thick or thin eggshell or eggs with multiple shell layers through an Upper Cretaceous stratigraphic interval in France. The researchers speculated that a mutation leading to fatal shell deformities may have spread through the population in defiance of natural selection until fatal eggshell anomalies were so common that the species went extinct. Alternatively, stressful living conditions could have prompted the formation of eggs with multiple shell layers as observed in modern turtles. They speculated that an overly favorable climate could have led to extreme fertility rates. The soaring dinosaur population became overcrowded until the stress from this overcrowding prevented dinosaurs from laying healthy eggs, leading to their extinction.
  Russel reviewed various proposed hypotheses for the extinct
caption: Deccan Traps volcanism was hypothesized to have been a main causative factor in the Cretaceous–Paleogene mass extinction
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