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Cretaceous Thermal Maximum
A period of climatic warming that reached its peak approximately 90 million years ago
The Cretaceous Thermal Maximum (CTM), also known as Cretaceous Thermal Optimum, was a period of climatic warming that reached its peak approximately 90 million years ago (90 Ma) during the Turonian age of the Late Cretaceous epoch. The CTM is notable for its dramatic increase in global temperatures characterized by high carbon dioxide levels.
A graph depicting data from the Phanerozoic Geological era, showing oxygen isotopes from present to 500 Ma. The isotope levels show an correlating increase in global temperatures due to glaciation and glacial retreat.
Measurements of the ratio of stable oxygen isotopes in samples of calcite from foraminifera from sediment cores show gradual warming starting in the Albian period and leading to the interval of peak warmth in the Turonian followed by a gradual cooling of surface temperatures to the end of the Maastrichitan age. During the Turonian, several pronounced but relatively short-lived cooler intervals punctuate the otherwise remarkably stable interval of extreme warmth.
Depiction of average planetary temperature of Earth over the past 500Ma. Note that the scale of 500-100Ma is halved to fit on the graph, with the Cretaceous Thermal Maximum occurring at the peak just before 100Ma.
^ abcdFoster, A., et al. "The Cretaceous Thermal Maximum and Oceanic Anoxic Event 2 in the Tropics: Sea- Surface Temperature and Stable Organic Carbon Isotopic Records from the Equatorial Atlantic." American Geophysical Union, Fall Meeting 2006. The Smithsonian/NASA Astrophysics Data System. Web. 20 Oct. 2009. <[adsabs.harvard.edu]>
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