Storm activity in ancient climates 2. An analysis using climate simulations and sedimentary structures

Severe storms generate sedimentary structures and textures that can be iden tified in the geologic record. A companion paper [PSUCLIM, this issue] desc ribes the genesis and distribution of both winter storms and hurricanes and their sensitivity to climatic and geographic variables. In this paper, a t otal of 90 storm deposits are compared to GENESIS climate simulations in or der to examine storm activity from the Permian to the Cretaceous and to eva luate the ability of the model to predict storms in ancient environments. A pproximately 70% of the observed deposits are predicted by the models. The majority of the missed deposits are associated with recognizable errors. If these specific sources of error are eliminated, the model predicts over 90 % of observed deposits. This degree of accuracy allows the assignment of ge nerative processes to individual deposits; however, causative differences b etween hummocky cross stratification and tempestite type deposits are not d istinguishable. The distribution of severe storms through Earth history var ies as a function of both continental geometry and climate. Elevated atmosp heric CO2 appears to homogenize the latitudinal distribution of storm depos its by expanding the area of hurricane genesis. Geography exerted the domin ant control on winter storm distribution and was responsible for a shift in the concentration of winter storm deposits from the Southern Hemisphere in the Early permian to the Northern Hemisphere in the mid-Cretaceous.