Transgressive regressive cycles in the John Henry Member, Straight Cliffs Formation southern Utah, USA

The John Henry Member of the Cretaceous Straight Cliffs Formation preserves marine and continental deposits along the margins of the Kaiparowits Plateau of southcentral Utah. The marginal marine deposits of the John Henry Member were deposited within a moderately high accommodation/high sediment supply setting, facilitating preservation of both tidally-dominated transgressive deposits and wave-dominated regressive deposits. Barrier island lagoonal facies, including lagoon, tidal inlets and washover fans, represent the transgressive system and wave-dominated deltaic shoreface, including lower to upper shoreface, foreshore, deflected mouth bar and fluvial facies, represent the regressive system. Sandstone facies, both transgressive and regressive, display statistically distinct modal sandstone compositions. Compositional trends mature from proximal (fluvial) to distal (marine) and also reflect strike variations (e.g. fluvial input point or location of deflected mouth bar) along the coastline.Transgressive and regressive facies in the John Henry Member combine to form atypical sequence stratigraphic surfaces and transgressive-regressive (T-R) cycles. Flooding surfaces in distal marine environments correlate into time-significant conformable contacts preserved as a process change (tide to wave energies) near the coastline. Wedges of transgressive facies are preserved between process change contacts and overlying wave ravinement surfaces (continuation of flooding surfaces), generating T-R cycles that do not correlate to downdip parasequences. The recognition of theses surfaces and different T-R cycles preserved due to accretionary transgressive deposits are critical to achieving accurate sequence stratigraphic interpretations of 4th -order cycles. Additionally, sequence boundary formation within this setting (high accommodation/sedimentation rates) does not follow standard models. Two surfaces within the John Henry Member record the deposition of tidal deposits over wave deposits. The first is composed of an unconformity, however it records a minor basinward shift in facies and is not interpreted as a result of a relative sea level fall. The second surface is conformable, however because of a significant basinward shift in facies, it is interpreted as forming during a slow relative sea level fall. These two surfaces demonstrate that an unconformable surface and a significant relative sea level fall are not always related.