Dune Stratigraphy
| Many of the dunes at Cape Henry are parabolic dunes. Coastal
parabolic dunes typically form as a foredune is breached and a blowout develops and
progresses to a parabolic dune form (series of diagrams to the right). Angle of repose
strata are formed as the nose develops a slipface and migrates downwind (a-a'). Dune arms
grow as a result of migrating wind ripples. This forms a series of arched layers composed
primarily of wind ripple laminae as shown in the schematic cross-sectional view of the
dune arm (b-b'). The GPR profiles below show two of the dunes surveyed. The internal structure of each dune shows discontinuous arch-shaped reflections under the highest part of the transect. Evidence for dune migration can be seen at 77th Street (purple lines). Irregular horizontal reflections characterize the dune arm surveyed at White Hill. The insets show transect orientation for each profile. |
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