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Numerical Modeling of Ancient Tides: The Impact of Paleogeographic Uncertainty on Shoreline Depositional Processes


The interaction of rivers, waves, tides and storms control the spatial and vertical heterogeneity of marginal marine reservoirs. These competing processes are controlled by tectonic and climatic setting, which impact key factors such as basin physiography, drainage basin size and sediment supply. However, reconstructing these factors and predicting shoreline processes for ancient depositional regions is subject to considerable uncertainty: multiple paleogeographic interpretations can invariably be constructed for a given region and time. The aim of this present study is to synthesize three case studies modeling ancient tides in a range of different geological settings; the Oligocene–Present evolution of SE Asia, the Cretaceous (Campanian) Western Interior Seaway of North America, and the Jurassic (Bajocian–Bathonian) Neuquén Basin. For each case study, using multiple paleogeographic scenarios indicates the sensitivity of modeled tides to paleogeographic uncertainty. On a regional scale (100–1000 km), the strength of tidal processes within a region/basin are controlled by: (1) the amount of tidal inflow and outflow; (2) the rate of change of bathymetry prior to tidal inflow into the basin; (3) the width versus depth of the region/basin and shoreline embayments, which controls tidal resonance; and (4) partitioning of tides relative to flow constrictions within the basin e.g islands and topographic highs. Tidal resonance also depends on the relative strength of diurnal versus semi-diurnal tidal constituents, which depends on latitude and landmass distribution. On a relatively local scale (1–100 km), tides are markedly sensitive to paleogeography uncertainty and are largely controlled by: (1) amplification due to frictional drag across the continental shelf; and (2) funneling between and into bathymetric constrictions e.g. islands and embayments. Our results indicate the capacity of numerical tidal modeling to efficiently test the implications of multiple paleogeographic scenarios on ancient shoreline processes, which in turn may decrease the uncertainty of depositional process predictions and reconstructions.