ABSTRACT

Eolian and subaqueous cross-strata cannot be distinguished reliably by many commonly cited criteria. They can, however, generally be distinguished by the characteristics of their component types of stratification, which represent processes of sorting and transport of the grain population on dunes. Eolian dune stratification types consist of grainflow cross-strata, grainfall laminae, and wind ripple-generated climbing translatent strata. Some of these types, especially translatent strata, have characteristics unique to the eolian realm. These same stratification types are found to compose some ancient cross-strata, and their occurrence confirms the eolian interpretations of pans of the Entrada (Jurassic), Navajo (Triassic-Jurassic), and Galesville (Cambrian) Formations, a well as revealing emergent islands in the Curtis Formation (Jurassic), previously considered to be totally marine in origin. Stratification types show a characteristic distribution on modern eolian dunes and differ in their relative abundances and structure on dunes of differing size and kind. These same relations allow some estimates of the type, shape, and original height of ancient dune deposits, as well as influencing the occurrences of surface features such as tracks and tipple forms. The geological record of stratification types and other dune features is greatly affected, however, by the extent of the post-depositional truncation of dunes.