When Is a Barrier Island Not an Island? When It Is Preserved in the Rock Record

Existing barrier island facies models are largely based on modern observations. This approach highlights the heterogeneous and dynamic nature of systems, but it overlooks processes tied to geologic time scales, such as multi-directional motion, erosion, reworking, their expressions preserved strata. Accordingly, this study uses characteristic outcrop from paralic strata Upper Cretaceous Straight Cliffs Formation in southern Utah update for motion preservation include time-scale processes. Results indicate that key distinguishing architectural elements systems have very little do with “island” morphology observed systems. Four associations used describe characterize these elements. Barrier islands occur association backbarrier fill (FA1) internally contain lower upper shoreface (FA2), proximal (FA3), tidal channel (FA4). Three main (barrier shorefaces, shoreface-dominated inlet fill, channel-dominated fill) independently or combination create stacked deposits. shorefaces record progradation, while records lateral migration, aggradation within inlet. bound by lagoons estuaries distinguished other deposits internal geometry, facies, position transgressive successions. Tidal processes, particular, migration reworking shoreface, also distinguish In sum, expands provides new recognition criteria account complex geometries time-transgressive,