Climate in Earth History Studies in Geophysics (1982) / Chapter Skim
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9 Long-Term Climate Oscillations Recorded in Stratigraphy
9 Long-Term Climate Oscillations Recorded in Stratigraphy
Pages 97-104
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From page 97... ...
Bedding phenomena visible at the outcrop level appear to correspond to climatic changes induced by the Earth's orbital perturbations in the 20,000-S00,000-yr range— the same forces that drove the glacial advances and retreats of the Pleistocene. Broader phenomena that must generally be synthesized from regional or global data suggest a possible climatic cycle in the 30-36 million years (m.y.)
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From page 98... ...
, the Triassic lake deposits of New Jersey (Van Houten, 1964) , and the Cretaceous and Eocene in central Italy, Schwarzacher bundles are in turn grouped into sets of four to six, representing about 0.5 m.y.
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From page 99... ...
In the Late Pleistocene record, for example, the eccentricity signal is strongest, the obliquity signal next, and the precessional signal weakest. In the Late Carboniferous cyclothems of Kansas another glacial hme eccentricity cycles—in particular, the 400,000-yr cycle—seem again to dominate the picture.
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From page 100... ...
. This pall oltotanical evidence for a once very different world is corroborated by the marine record: The present ocean's warm waters are confined to a thin surficial layer in the lower +2 0 - 2 d o PoD A- PALEOfEMPERATURES l 0 10 20 FIGURE 9.2 Paleotemperatures derived from oxygen isotope ratios in calcitic fossil skeletons, assuming constant oxygen isotope ratios in seawater.
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From page 101... ...
Bottom waters are close to the freezing point throughout the oceans, and the mean termperahrre of the oceanic water masses lies at about 3~C While we do not have reliable measurements of paleotemperaturex—oceanic or otherwise—for the ice ages of the Paleozoic and Precambrian, it seems likely that their oceans had a temperature and structure rather similar to that of today In contrast, studies of oxygen isotopes from Cretaceous oceanic deposits (e.g., Douglas and Sat in, 1975) show that the temperatures of the hut k of the Cretaceous ocean masses lay in the vicinity- of 15°C, i e., that the mean temperature of the oceans averaged some 100 above that of the present ones.
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From page 102... ...
For the reasons why high sea levels should coincide with greenhouse states, see brlov . Oceanic Aeration The ocean of our day is moderately well oxygenated throughout, so that animal life, dependent on aerobic respiration, is possible on almost all bottoms and throughout almost all of the water mass.
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From page 103... ...
This is here sought in hypothetical cycles of mantle convection, which drive sea levels and atmospheric carbon dioxide content by independent pathways linked by a feedback mechanism (weathering)
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From page 104... ...
. Oxygen and carbon isotope analyses of Cretaccous and Tertiary microfossils from Shatsky PI c and other sites in the North Pacific Ocean, in Initial Reports of Deep Sea Drilling Project, Vol.
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