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The stepwise genesis and evolution of modern shelf sand ridges are investigated through chronostratigraphic analysis of four separate study sites on the New Jersey Atlantic shelf, ranging in depth from less than 4 meters (shoreface-attached ridge) to over 45 meters (detached ridge). Radiocarbon age-dated vibracores and high-resolution seismic surveys facilitated construction of a series of chronostratigraphic cross-sections of these 1 by 5 km-scale and greater ridges, which can range in vertical thickness to 10 meters. These data provide compelling support to an earlier morphodynamic model suggesting that shoreface-attached ridges may originate from ebb-tidal deltas and eventually detach from the shoreline during coastal transgression. A key element of the morphodynamic model involves cutting of the adjacent swale by an obliquely migrating tidal-inlet channel.

However, notable yet transitional differences exist between shoreface, nearshore, and offshore ridges in terms of age, microfaunal content, bathymetric profile, and cross-sectional area. This implies that ridges change considerably following coastal detachment. During this final phase, which we term ridge evolution, the ridges may migrate, change orientations, and possibly cannibalize earlier ridge and inlet-channel-fill complexes. This stage may be the most important in terms of what is preserved in the sedimentary record. Understanding the dynamic nature of these long-lived, transgressive shelf sand ridges may help resolve some of the debate regarding analogous ancient, stratigraphically-isolated marine sand bodies.

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