Spatial and temporal evolution of a coastal erg margin: the Middle Jurassic Page Sandstone, southern Utah, USA

Aeolian deflationary events are erosive to static stages where sediment supply is insufficient to support bedform migration and preservation in the rock record. In the vicinity of shallow‐marine environments, inland rises of relative water table and associated generation of deflationary super surfaces may be driven by the onset of transgression phases. However, despite this link being widely recognised in ancient systems, current genetic models for coastal erg margins fail to account for stratigraphical complexities and spatial changes in aeolian sedimentary architectures across their different depositional belts. This study addresses this gap by investigating the spatio‐temporal evolution of the Middle Jurassic Temple Cap Formation and Page Sandstone and their relationship with the contemporaneous shallow‐marine strata of the Carmel Formation, in southern Utah, USA. A set of twenty observed lithofacies grouped into eight architectural elements were identified in seven sedimentary logs and four outcrop panels collected across two palaeoshoreline‐perpendicular transects. Spatio‐temporal analysis of the documented stratigraphical framework reveals two major erg‐building phases, each interpreted as the product of a regressive system tract, and intercalated with intervening transgressive marine system tracts. Depositional models incorporating geometries of aeolian architectural elements and their relationships with marine units are proposed for both regressive and transgressive scenarios. Regressive system tracts are dominated by superimposed draa cosets in coastal erg centre environments that grade laterally into simple transverse bedform sets as sediment availability decreases towards marginal regions. Transgressive system tracts are, conversely, the scene of significant sediment remobilisation through tidal ravinement in erg margin regions and regional deflationary super surface development further inland. Detailed documentation of sedimentary architecture within aeolian–marine sequences, and investigation of the variable expression of their bounding surfaces, helps constraining the depositional record of these complex systems. Exploring the interplay between aeolian and marine processes and their associated stratigraphical products improves our ability to populate reservoir models and predict facies distribution in analogous subsurface systems.