Do detailed hydrodynamic and sedimentologic data aid prediction of nearshore
stratigraphy? Examples from the Duck94 Nearshore Field Experiment
Smith, J. B., Drake, T. G., Gallagher, E. L. and Elgar, S., 1995, Do
detailed hydrodynamic and sedimentologic data aid prediction of nearshore
stratigraphy? Examples from the Duck94 nearshore field experiment: Geological
Society of America Program, Annual Meeting, New Orleans, Louisiana, 6-9
November 1995
Nearshore vibracores and box cores collected during the Duck94 Nearshore
Field Experiment (August-October 1994) near Duck, North Carolina, offer
a unique opportunity to study sedimentary structures and stratigraphy and
their relation to detailed bed-elevation and hydrodynamic data. Most cores
were taken within a few meters of a cross-shore transect of wave, current,
and bed-elevation sensors extending about 800 m from the shoreline to 8
m water depth. Significant bathymetry changes occurred during the experiment.
In particular, winds from a mid-October nor'easter produced 4.5 m waves
and longshore currents exceeding 1 m/s. During the storm a single linear
summer bar migrated 100 m offshore, eroding about 1.5 m from its former
position. Cores penetrating newly-deposited bar sands do not display strong
evidence (i.e. crossbeds) of migrating bedforms, despite bed-elevation data
and ancillary observations indicating that megaripples were present. Synthetic
stratigraphies generated from bed elevation time-series were used to construct
histograms of strata thickness for comparison with similar histograms from
cores. Synthetic thickness histograms show greatly increased frequencies
for depositional events creating strata less than 1cm thick, and reduced
frequencies for thicker strata, relative to data from cores obtained both
by visual inspection and x-ray. Hypotheses for these discrepancies and implications
for stratigraphic studies of nearshore barrier island deposits will be discussed.
Supported by US Army Corps of Engineers Waterways Experiment Station, Coastal Engineering Research Center