Geology Reference
In-Depth Information
Fig. 12.14
Stratigraphic sections for Price and Capers Inlets,
SC (From Tye and Moslow
1993
). Note that these inlets did not
migrate; rather their main channels were defl ected south due to
the dominant southerly longshore transport and then breached
back to a straight channel course
landward-dipping foresets produced by swash bar
migration.
2. A proximal delta region is dominated by a sedi-
mentary sequence produced by the shifting of the
main ebb channel. These deposits are up to 20 m
thick and have a sharp contact with the underlying
Pleistocene sediments. The basal units consist of
seaward dipping, cross-bedded, medium to coarse
sand with shells grading upward into a well-sorted,
planar-bedded fi ne sand.
3. Distal delta deposits are 1-4 m thick and consist of
an overall coarsening upward sequence that inter-
fi ngers with seaward shoreface sediments. The
wave-dominated platform is characterized by
planar-bedded to landward-oriented, cross-bedded,
very well-sorted, fi ne sand. Coarse shell hash layers
and burrowing are common attributes.
Thus, the ebb-delta deposits exhibit a sharp basal
contact with the shoreface and an overall fi ning-upward
sequence except for the distal portion of the delta that
coarsens upward. Local coarsening of the sediment
may also occur due to the migration of tidal channels
or the onshore movement of swash bars.
Nelligan's (
1983
) study at Breach Inlet, north of
Charleston Harbor, SC, recorded the stratigraphy of an
ebb delta during a phase of tidal-channel abandonment
and encroachment of landward migrating bar com-
plexes (Fig.
12.16
, see also Fig.
12.5a
). The delta litho-
some contains a tidal-channel fi ll sequence that is
similar to that of North Edisto adjacent to the barrier
