Abstract

In the Rogers Canyon area of the Kaiparowits Plateau, the John Henry Member of the Cretaceous Straight Cliffs Formation preserves both regressive shoreface and fluvial channel environments, and transgressive lagoonal barrier-island system environments. Regressive units, including complete successions of the shoreface facies association (distal to proximal lower shoreface, middle shoreface, upper shoreface and foreshore) and the channel facies association (defected mouth bar, fluvial channels and coastal plain) are interpreted as parts of a progradational, wave-dominated, defected deltaic system. Transgressive units are comprised of the lagoonal facies association (lagoonal fill) and inlet facies association (tidal inlets and washover fans), which aggraded during relative sea level rise and infilled as relative sea level slowed and began to fall. Thick (up to 30 m) accumulations of lagoonal successions require a balance between sediment supply and accommodation, in order to initially deposit sediment and to protect it from subsequent erosion. A coastal onlap or relative sea level curve was generated, and this curve displays higher-resolution shoreline shifts than previously recognized for the John Henry Member. A combination of internal (autogenic) and external (allogenic) forces are evaluated as potential controlling factors. Autogenic (sedimentation, shoreline profile) and allocyclic (accommodation) forces create the internal variation within each facies association. The transition between regressive and transgressive units is interpreted as recording overlapping 4^th order eustatic and tectonic signatures.