| Description |
Paralic depositional environments link terrestrial and marine settings and include a variety of environments such as deltas, lagoons, estuaries, barrier islands, tidal deltas, and strand plain shorelines. Influenced by both terrestrial and marine processes, these settings are complex and variable, which both limits and favors their preservation over various timescales through an interplay of deposition, motion, reworking, and ravinement. This dissertation addresses paralic depositional environments with analysis of both modern and ancient examples. An unusually thick succession of marine, paralic, and nonmarine strata from the Cretaceous of southern Utah (John Henry Member, Straight Cliffs Formation) is documented, with a focus on regressive-transgressive cycles and evolution of this part of the Western Interior Seaway, including controls on accommodation and sediment supply. This outcrop analysis leads to a detailed inquiry into barrier island systems, which is addressed by facies models and recognition criteria for three types of barrier island expressions. Databases of modern barrier islands (mapped in Google Earth) and ancient examples from the literature were assembled to further investigate links and disconnects between modern and ancient systems. This analysis is a first step toward developing paleomorphodynamic relationships to predict barrier island dimensions. It also highlights the uncertainty surrounding comparisons between modern and ancient barrier islands, which stems from the complexity of controls on modern barrier island motion and morphology. Additional analysis of the modern database challenges a long-held assumption in coastal geomorphology, which suggests that barrier island shape is a function of tidal range and wave height. Based on shape parameters applied to 702 mapped barrier islands and spits, I determine that tidal range and wave height control <10% of barrier island morphology. Substantial complexity exists in the other 90% of controlling factors, justifying the need for future studies that test the relationship between modern and ancient barrier island systems. |
