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Evaluating Paleoclimate Indicators Using Previous HitClimateNext Hit Envelopes

 

Moore, Thomas L.1, Roy E. Plotnick2, Martin Perlmutter3, Judith Totman Parrish4 (1) PaleoTerra, Bolingbrook, IL (2) University of Illinois at Chicago, Chicago, IL (3) Chevron, Houston, TX (4) University of Idaho, Moscow, ID

 

A basic method in paleoclimate studies is to infer Previous HitclimateNext Hit on the basis of the distribution of paleoclimate indicators, such as evaporites and coals. Unlike many quantitative geochemical techniques (such as using isotopes to yield temperatures), many indicators yield only generalizations, such as “hot” or “wet.” These limited interpretations exist because most sedimentary indicators represent non-unique Previous HitclimateNext Hit conditions—that is, an indicator could represent a wide range of Previous HitclimateNext Hit states. These simplifications present difficult problems when comparing paleoindicators to modern climates or Previous HitclimateNext Hit models or using models to predict the distribution of sediments.

 

We present the concept of Previous HitclimateNext Hit envelopes to generate a more quantitative climatic interpretation of sedimentary indicators. A Previous HitclimateNext Hit envelope represents a calibrated range of two or more Previous HitclimateNext Hit-related parameters, such as temperature and precipitation, for a particular sediment type, such as an evaporite. Unlike most approaches that use annual averages, the envelope uses monthly averages because many indicators do not form over the entire year. Envelopes can be expressed as presence/absence distributions or as probability distributions. These distributions can then be directly applied to Previous HitclimateNext Hit data or Previous HitclimateNext Hit model results.

 

For this study, we focused primarily on evaporites and histosols to evaluate the applicability of the Previous HitclimateNext Hit envelope approach. We calibrated the indicators by using their modern distributions and modern Previous HitclimateNext Hit data and then applying the envelopes to Cretaceous and Permian Previous HitclimateTop simulations to predict indicator distributions.

 

AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California