--> Abstract: Regional Impacts of Orbital Cycles from the Cretaceous World, by Thomas L. Moore, Roy Plotnick, and Martin Perlmutter; #90078 (2008)

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Regional Impacts of Orbital Cycles from the Cretaceous World

Thomas L. Moore1, Roy Plotnick2, and Martin Perlmutter3
1PaleoTerra, Bolingbrook, IL
2University of Illinois, Chicago, Chicago, IL
3Chevron, Inc, Houston, TX

The response of Earth’s climate system to changing orbital cycles is complex. In general, the distribution of solar insolation on the Earth provides a reasonable estimate for surface temperatures. Of the three orbital cycles, precession, when coupled with high eccentricity, has the greatest impact on insolation. Eccentricity and obliquity by themselves provide only relatively weak controls. Geologic evidence of these weaker cycles, however, is commonly interpreted from the statistical analysis of the stratigraphic record. This apparent conflict exists because the primary impact of orbital cycles is on insolation and surface temperatures. Deposition, however, is directly controlled by the hydrologic cycle, which is affected not only by insolation and surface temperature, but also by continental geography and ocean circulation.

We have run over 20 climate circulation models for the Cretaceous (90MA) with various orbital states using the Fast Ocean-Atmosphere Model. These simulations allowed us to isolate the influence of specific orbital parameters on climate. Three approaches were used to analyze the results. We first tested whether there was a statistically significant difference between the simulations. Areas without significant changes between models would not be expected to leave a detectable sedimentary record. We then evaluated correlations between insolation and the climatic difference found in the models themselves. Finally, we examined the unique regional impacts that are linked to geography.

Our results show that in cases of high eccentricity, precession dominates the impacts on climate. The results also show that obliquity can have an impact on polar temperatures and tropical precipitation rates, depending on continental geography.

 

AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas