There is some correlation between the heavy mineral content and the 
median grain-size of the total sample. Sediments with sieve medians near 
1/8 mm usually have the greatest amounts of heavy minerals, while the 
abundance decreases for coarser and finer sediments. However, location and 
season appear to be as important as size in determining the concentration 
of heavies. As shown in Figure 1, the greatest percentages occur on the 
beach foreshore, and the least in the adjacent surf zone. Another band of 
heavy-rich sediments occurs just outside of and parallel to the surf zone, 
There is a pronounced seasonal variation in the percentage of heavy 
minerals, particularly on the beach foreshore, where the apparent abundance 
of heavy minerals increases during the winter when the beaches are cut 
back. A possible explanation for this apparent seasonal migration of heavy 
minerals lies in the transportation of light minerals fromthe beach foreshore 
to deeper water during the winter and back again during the summer. Since 
only surface samples were used in this study, deposition of light minerals 
results in apparent decrease in heavy mineral concentrations, and vice versa. 
The extreme variability in the amount of heavy minerals both with 
location on the beach and with time raises some question as to the inter- 
pretation of heavy mineral suites in beach and nearshore studies. Certainly, 
no simple relationship exists between the kind and amount of any particular 
mineral specie and its position on the beach. 
ORBITAL CURRENT METER 
During the last three months laboratory experiments for the evaluation 
of the coefficient of virtual mass have been completed. These experiments 
indicate that the instrument is sensitive to both drag and accelerative 
forces, but that in most instances the orbital velocity of wave motion can 
be interpreted without undue interference from virtual mass. 
DEFINITION OF DEPOSITIONAL ENVIRONMENTS 
It was thought that the following definitions, which were prepared by 
F, P. Shepard relative to investigation of sedimentation in the northern 
Gulf of Mexico for the American Petroleum Institute would be of interest 
in beach erosion studies. Accordingly, they are given below: 
Open Bay or Bight - A broad indentation between two headlands or points, 
the bays being sufficiently open so that waves coming directly into the bay 
are essentially the same in height near the center of the bay as on open 
portions of the coast. 
Hooked bay - Similar to the preceding but having only one headland. 
Estuary - A bay extending roughly transverse to the coast and having 
an outline similar to a typical river valley contour. Ecologically a great 
difference may exist depending on whether or not a stream enters the head 
of the estuary. 
7 
