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

Severe storms generate sedimentary structures and textures that can be identified in the geologic record. A companion paper [PSUCLIM, this issue] describes the genesis and distribution of both winter storms and hurricanes and their sensitivity to climatic and geographic variables. In this paper, a total of 90 storm deposits are compared to GENESIS climate simulations in order to examine storm activity from the Permian to the Cretaceous and to evaluate the ability of the model to predict storms in ancient environments. Approximately 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 generative processes to individual deposits; however, causative differences between hummocky cross stratification and tempestite type deposits are not distinguishable. The distribution of severe storms through Earth history varies as a function of both continental geometry and climate. Elevated atmospheric CO₂ appears to homogenize the latitudinal distribution of storm deposits by expanding the area of hurricane genesis. Geography exerted the dominant 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.