A NOVEL CO2 PARTIAL PRESSURE-BASED METHOD OF ESTIMATING PALEO-ELEVATION FROM FOSSIL PLANTS

Currently the majority of methods used to estimate paleo-elevation are based on the relationship of temperature with altitude, and for this reason, are inherently climate-sensitive. It remains difficult therefore to decipher the effects of tectonic uplift from broad scale global climatic cooling, which hampers our ability to evaluate or constrain theories relating to tectonic and climatic evolution. The reduction in CO₂ partial pressure with altitude exerts a physiological limitation on plant photosynthesis, which is compensated for, in many species, by an increase in stomatal frequency (density and index) and altered stomatal distribution. This strong inverse relationship between stomatal frequency and atmospheric CO₂ partial pressure, has been repeatedly demonstrated experimentally and also historically over the past 200 years of anthropogenic CO₂ rise and has been successfully utilized to reconstruct paleo-CO₂ trends on timescales of centuries to millennia. The accuracy with which paleo-CO₂ concentrations can be estimated from sub-fossil and fossil stomata, and the observation that stomatal density and index increase with decreasing CO₂ partial pressure with altitude, offers the potential of utilizing this relationship as a novel paleo-altimeter. A model for estimating paleo-elevation from fossil stomatal frequency will be presented with preliminary supporting data and the implications of this new method will be discussed.