Abstract

Isostatic uplift of tectonically stable, passive margin lithosphere can preserve a record of paleo-shoreline position by elevating coastal geomorphic features above the influence of nearshore wave activity. Conversely, depositional ages and modern elevations of these features can provide valuable information about the uplift history of a region. We present a numerical model that combines sea-level oscillation, subaerial exposure, a precipitation-karstification function, and isostatic uplift to explore the dynamic geomorphic behavior of coastal carbonate landscapes over multiple sea-level cycles. The model is used to estimate ages of coastal highstand depositional features along the Atlantic coast of north Florida. Numerical simulations using current best estimates for Pleistocene sea-level and precipitation histories suggest ages for Trail Ridge (1.44 Ma), the Penholoway Terrace (408 ka), and the Talbot terrace (120 ka) that are in agreement with fossil evidence. In addition, model results indicate that the rate of karstification (void space creation or equivalent surface lowering rate) within the north Florida platform is ∼3.5 times that of previous estimates (1 m/11.2 k.y. vs. 1 m/38 k.y.), and uplift rate is ∼2 times as high as previously thought (0.047 mm/yr vs. 0.024 mm/yr). This process has implications for landscape evolution in other carbonate settings and may play an underappreciated role within the global carbon cycle.

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