Cretaceous Thermal Maximum

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Cretaceous Thermal Maximum, also known as Cretaceous Thermal Optimum, was a period early in the Late Cretaceous notable for its dramatic increase in global temperatures.

A graph depecting data from the Phanerozoic Geological era, depicting the increased global temperatures during the Cretaceous Thermal Maximum around 90Ma.


Carbon dioxide levels rose to over 1000 parts per million (compared with the recent pre-industrial average of 280 ppm), which resulted in a significant increase in the greenhouse effect, and elevated temperatures.[1] In the seas, the glassy form foraminifera predominated, a key indicator of higher temperatures. The Cretaceous Thermal Maximum occurred during the Cenomanian/Turonian transition based from the fact that there was a major disruption to global climate.[2] It was the most extreme disruption of the carbon cycle recorded in the past 100 million years.[3][4]


Late Cenomanian sea surface temperatures in the equatorial Atlantic Ocean (~33 °C) were substantially warmer than today (~27-29 °C).[3] They may have been as high as 36 °C.[5] The interval of peak warmth in the Turonian has been attributed to very high atmospheric CO2 and possibly enhanced by the changing geography of the oceans including an "Atlantic Gateway".[4] However, during the Turonian age, several pronounced but relatively short-lived cooler intervals punctuate this otherwise remarkably stable interval of extreme warmth and shows that rapid tropical sea surface temperature changes occurred during the Cretaceous thermal maximum, and implies that even the mid-Cretaceous "super-greenhouse" climate may have been less stable than previously thought.[3]

See also[edit]


  1. ^ Atmospheric carbon dioxide levels for the last 500 million years, PNAS April 2, 2002 vol. 99 no. 7 4167-4171, DOI:10.1073/pnas.022055499
  2. ^ Norris, Richard (2018). "Cretaceous Thermal Maximum ~85-90 Ma." Scripps Institution of Oceanography. Accessed 20 September 2018.
  3. ^ a b c Foster, 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. <>
  4. ^ a b Poulsen, Christopher J., Andrew S. Gendaszek, and Robert L. Jacob. "Did the rifting of the Atlantic Ocean cause the Cretaceous thermal maximum?" Geology 31.2 (2003): 115-118. Web. 20 Oct. 2009. <>.
  5. ^ Wilson, Paul A., Richard D. Norris, and Matthew J. Cooper. "Testing the Cretaceous greenhouse hypothesis using glassy foraminiferal calcite from the core of the Turonian tropics on Demerara Rise." Geology 30.7 (2002):607-610. Web. Oct.2009.<>.