Temporal variation in the wavelength of hummocky cross-stratification: Implications for storm intensity through Mesozoic and Cenozoic

Hummocky cross-stratification is believed to be one of the diagnostic sedim entary structures of storm-dominated shallow-marine environments. The wavel ength of this stratification increases with the increase in bed thickness o f tempestites and decreases with the increase in paleowater depth. The humm ocky cross-stratification wavelength is interpreted to be a function of the orbital diameters of storm-induced oscillatory currents near seafloors and may reflect the intensity of storm waves. Temporal variation in the wavele ngth was investigated as a proxy for storm intensity through Mesozoic and C enozoic time. The hummocky cross-stratification wavelength shows a secular change, and a major peak in the middle Cretaceous. This variation largely c orresponds to one of the two greenhouse and icehouse supercycles of global environmental changes during the Phanerozoic and provides a geologic perspe ctive of the possible increase in storm intensity with an ongoing greenhous e phase in the future.