Estimating tectonic uplift of the Cape Fear Arch (south‐eastern United States) using reconstructions of Holocene relative sea level

Abstract

We use relative sea‐level (RSL) reconstructions and a spatiotemporal statistical model to estimate the rate of uplift of the Cape Fear Arch, a Mesozoic structural high, during the last ∼4000 years. We reconstructed RSL using 12 radiocarbon‐dated samples of basal salt‐marsh sediment preserved at Elizabeth Creek Marsh on the Cape Fear River. The new data show that RSL rose by ∼3 m during the past ∼4.6 ka at an average rate of 0.67 ± 0.12 mm a −1 . RSL reconstructions from other sites in southern North Carolina (which have rates of 0.91 ± 0.10 to 0.84 ± 0.24 mm a −1 ) probably show ( P > 0.9) higher rates of regional RSL rise for the same period, while sites from northern South Carolina (which have rates of 0.72 ± 0.17 to 0.80 ± 0.21 mm a −1 ) probably ( P > 0.67) show the same. We attribute the differences between Elizabeth Creek Marsh and neighboring regions to uplift of the Cape Fear Arch, which we estimate to be 0.24 ± 0.15 mm a −1 . Uplift of the arch may be responsible for lower rates of 20 th century RSL rise recorded by the Wilmington tide gauge relative to rates measured elsewhere along the US mid‐Atlantic coast.

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