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

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doi: 10.1016/j.gr.2015.12.004
Author(s): Nimura, Tokuhiro; Ebisuzaki, Toshikazu; Maruyama, Shigenori
Author Affiliation(s): Primary:
Japan Spaceguard Association, Ibara, Japan
Other:
RIKEN, Japan
Tokyo Institute of Technology, Japan
Volume Title: Gondwana Research
Source: Gondwana Research, Vol.37, p.301-307. Publisher: Elsevier on behalf of International Association for Gondwana Research, Amsterdam and Kochi, International. ISSN: 1342-937X
Note: In English. 51 refs.; illus., incl. 2 tables, sketch map
Summary: We have identified iridium in an ∼ 5 m-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" fEX. 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 ∼ 100 pc and the central density of over 2000 protons/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 -9.3 W m-2, the dark cloud would have caused global climate cooling in the last 8 Myr 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.
Year of Publication: 2016
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
ODP Ocean Drilling Program
Key Words: 02 Geochemistry; 12 Stratigraphy, Historical Geology and Paleoecology; Atlantic Ocean; Chicxulub Crater; Climate change; Cooling; Cretaceous; DSDP Site 463; DSDP Site 525; Dark clouds; Deep Sea Drilling Project; IPOD; Impact features; Iridium; Isotope ratios; Isotopes; Leg 113; Leg 145; Leg 62; Leg 74; Marine environment; Marine sediments; Mass extinctions; Mathematical methods; Maud Rise; Mesozoic; Metals; Mid-Pacific Mountains; North Pacific; Northwest Pacific; O-18/O-16; ODP Site 690; ODP Site 886; Ocean Drilling Program; Oxygen; Pacific Ocean; Paleoclimatology; Paleoecology; Pelagic environment; Platinum group; Sediments; South Atlantic; Southern Ocean; Stable isotopes; Upper Cretaceous; Walvis Ridge; Weddell Sea; West Pacific
Coordinates: S290415 S290414 E0025908 E0025907
Record ID: 2017029073
Copyright Information: GeoRef, Copyright 2017 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands