End-cretaceous cooling and mass extinction driven by a dark cloud encounter

Tokuhiro Nimura, Toshikazu Ebisuzaki, Shigenori Maruyama

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

We have identified iridium in an ~5m-thick section of pelagic sediment cored in the deep sea floor at Site 886C, in addition to a distinct spike in iridium at the K-Pg boundary related to the Chicxulub asteroid impact. We distinguish the contribution of the extraterrestrial matter in the sediments from those of the terrestrial matter through a Co-Ir diagram, calling it the "extraterrestrial index" f EX. This new index reveals a broad iridium anomaly around the Chicxulub spike. Any mixtures of materials on the surface of the Earth cannot explain the broad iridium component. On the other hand, we find that an encounter of the solar system with a giant molecular cloud can aptly explain the component, especially if the molecular cloud has a size of ~100pc and the central density of over 2000protons/cm3. Kataoka et al. (2013, 2014) pointed that an encounter with a dark cloud would drive an environmental catastrophe leading to mass extinction. Solid particles from the hypothesized dark cloud would combine with the global environment of Earth, remaining in the stratosphere for at least several months or years. With a sunshield effect estimated to be as large as -9.3Wm-2, the dark cloud would have caused global climate cooling in the last 8Myr of the Cretaceous period, consistent with the variations of stable isotope ratios in oxygen (Barrera and Huber, 1990; Li and Keller, 1998; Barrera and Savin, 1999; Li and Keller, 1999) and strontium (Barrera and Huber, 1990; Ingram, 1995; Sugarman et al., 1995). The resulting growth of the continental ice sheet also resulted in a regression of the sea level. The global cooling, which appears to be associated with a decrease in the diversity of fossils, eventually led to the mass extinction at the K-Pg boundary.

Original languageEnglish
JournalGondwana Research
DOIs
Publication statusAccepted/In press - Aug 3 2015
Externally publishedYes

Fingerprint

iridium
mass extinction
Cretaceous
cooling
extraterrestrial matter
strontium
asteroid
sediment
solar system
stratosphere
ice sheet
deep sea
global climate
stable isotope
seafloor
diagram
sea level
fossil
anomaly
oxygen

Keywords

  • Dark cloud encounter
  • End-Cretaceous
  • Global cooling
  • Mass extinction

ASJC Scopus subject areas

  • Geology

Cite this

End-cretaceous cooling and mass extinction driven by a dark cloud encounter. / Nimura, Tokuhiro; Ebisuzaki, Toshikazu; Maruyama, Shigenori.

In: Gondwana Research, 03.08.2015.

Research output: Contribution to journalArticle

Nimura, Tokuhiro ; Ebisuzaki, Toshikazu ; Maruyama, Shigenori. / End-cretaceous cooling and mass extinction driven by a dark cloud encounter. In: Gondwana Research. 2015.
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