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Climate in Earth History Studies in Geophysics (1982) / Chapter Skim
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8 The Terminal Cretaceous Extinction Event and Clilmatic Stability
Pages 90-96

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From page 90...
... This cooling trend started about 60 million years ago (Ma) and has been particularly well documented in changes of the oxygen isotopic composition of fossil carbonate shells (Savin, 1977)
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From page 91...
... A geologically instantanem~s extinction of virtually the entire late Cretaceous oceanic calcareous phytoplankton has been well documented (Figure 8.1) ; this was followed by blooms of neritic taxa such as Braarudasahaera and the dina % TERTIARY 10 70 30 40 so so 70 so so no so co 70 on 50 40 JO 7a lo % CRETACEOUS o m m ar 3 FIGURE 8.1 Replacement of the late Cretace us by early Tertiary Cd careo s nam~ofoxsils withm 70 cm of sediment thickness at DSDP Site 384, western North Atlantic (after Thierstein and Okada, 1979)
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From page 92...
... are considered too slow to be solely responsible for the quite sudden extinction events; such sea-level changes may have been instrumental however in triggering positive climatic feedback mechanisms or the isolation of ocean basins and their reconnechon with the world oceans. HISTORY OF CARBONATE DEPOSITION Bramlettes (1965)
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From page 93...
... STABLE ISOTOPES Some of the most important information known about climates in the late Mesozoic is derived froth comparatively few studies on the oxygen isotopic composition of fossil carbonate shells. These studies were concentrated on an evaluation of major stratigraphic trends and paleolatitudinal gradients (Frakes, 1979)
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From page 94...
... How different were late Cretaceous climates from Pleistocene ones? From a late Phanerozoic viewpoint, today's oceans are characterized by their small and highly dispersed areal coverage, by their pronounced temperature stratification into a thin, warm surface layer and a large cold deep layer, and by vigorous meridional surface circulation, leading to a strong geographical separation of fertility The deep-water reservoir —2 _]
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From page 95...
... claim for a significantly lowered inclination of bbe Earth's rotational axis? A number of open questions concerning late Cretaceous climates can be answered by careful study of available sediments and fossils and by using available techniques, whereas others will have to be addressed by way of analogy and inference from the longer-range Phanerozoic climatic history of the Earth.
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From page 96...
... . The Cretaceous/Tertiarv boundary event in tbe North Atlantic, in Inihal Report3 Deep Sea Drilling Project 43, U.S.
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Key Terms

  • oxygen isotopic
  • tertiary boundary
  • deep sea
  • isotopic composition
  • surface waters

  • extinction event
  • climatic feedback
  • feedback mechanisms
  • oceanic surface
  • climatic stability

  • sensible heat
  • cooling trend
  • terminal cretaceous
  • heat transport
  • cretaceous climates

  • carbonate shells
  • sea drilling
  • ocean basins
  • evolutionary change
  • benthic foraminifera

  • stable isotopic
  • ous tertiary
  • oceanic sensible
  • cretao ous
  • isotopic data

  • boundary clay
  • stable isotopes
  • latitudinal surface
  • north atlantic
  • fossil carbonate


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