Controls on Eolian Facies Architecture, Middle Jurassic Page Sandstone, Colorado Plateau

Abstract

Eolian systems to not fit simply into basin sedimentation models developed for marine/coastal sequences. Therefore a new conceptual framework was developed linking eolian basin-scale sedimentation patterns to conditions and events within and external to the eolian environment. Controlling factors at this scale are eolian sediment budget, sand supply, water-table fluctuation, and subsidence. These parameters and their relative rates predict eolian system type, genetic stratigraphy, mode of preservation, and resulting facies architecture. This conceptual model allows interpretation of the genetic or event stratigraphy of an eolian sandstone and inference of basinal conditions during its formation. The Page Sandstone, an erg system adjacent to the Middle Jurassic Carmel interior seaway, consists of two laterally continuous accumulations of dry eolian systems, relatively uninterrupted by super surfaces (Harris Wash and upper Thousand Pockets); these are separated by a contrasting eolian condensed zone, which consists of lenses of dry dunefield accumulations truncated by multiple wet super surfaces. The Harris Wash and upper Thousand Pockets represent times of high sand supply and positive sediment budget, with water table well below the sediment surface during a relative lowstand of the Carmel sea. The condensed zone indicates a time of low sand supply, a high but fluctuating watermore » table, and a sediment budget fluctuating from positive to negative. It corresponds to a relative Carmel sea-level rise. In the Page Sandstone single or multiple super surfaces in the eolian system correspond to maximum flood surfaces in the marine system. In contrast, relative sea-level lowstands are represented by erg accumulations uninterrupted by hiatal surfaces.« less