122 
PACIFIC SCIENCE, Vol. XVII, January 1963 
Fig. 8. Bathymetry and sample locations along Ka- 
paa Reef. Dotted areas depict breaker zone on outer 
edge of reef platform. The circulation pattern of wave 
generated currents over the reef is shown in the inset. 
(Bathymetry compiled from Board of Harbor Com- 
in the rock results from a monomineralic species ; 
in the biogenous material of the original deposit. 
The presence of the single carbonate mineral spe- 
cies may be most easily accounted for by assum- 
ing (1) the inversion of an original aragonite 
component to calcite (see Jamieson, 1953); 
and (2) alteration of magnesium-rich to mag- 
nesium-poor calcite by the diagenetic loss of 
magnesium ions from an original magnesium- 
rich calcite component (see Chave, 1954£). The 
time required for such processes to be carried to 
completion, and the present physiographic posi- 
tion of this fossil dune, both suggest that it is 
considerably older than the neighboring beach 
rock. 
; 
KAPAA — A WINDWARD REEF AND BEACH 
Kapaa Reef lies along the windward east coast 
of Kauai, and has an overall length of about 2Vi 
miles along the north-south trending coastline 
in the vicinity of the town of Kapaa. It is a 
fringing reef and is divided into northern and 
southern portions by an inlet through the reef 
where two small streams enter the ocean near 
the center of the town. The Kealia River enters 
the ocean about 1 mile north of Kapaa, and the 
Wailua River enters the coastal embayment to 
the south of the reef. Although both rivers have 
appreciable runoff, they contribute relatively lit- 
tle sand-sized material to the littoral zone. 
North Kapaa Reef is approximately 4,000 ft 
long, and varies in width from about 400 ft at 
its northern end to 1,500 ft at the southern end, 
where it is terminated by the inlet (Fig. 8). 
The reef platform has an average depth of about 
2 V 2 ft below mean sea level, and the tide has a 
diurnal range of 1.8 ft. The inshore edge of the 
reef is bordered by a beach of medium- to | 
coarse-sized calcareous sand. The beach has an 
average height of berm above mean sea level of 
about 6 V 2 ft, and has a total thickness of sand 
above the reef platform of about 8 ft. A rem- 
nant toe of beach rock, which outcrops inter- 
mittently on the reef flat 10-40 ft offshore from 
the present beach (Fig. 9), indicates a slight re- 
cession of the beach. The seaward portion of the 
missioners Survey of 1919; photomosaic by R. M. 
Towell Inc., 1950; and miscellaneous soundings in 
1957 (?) by H. V. Frasier, Hawaiian Dredging Co., 
and in 1959 by Sam Keala, Jr., of Lihue Plantation). 
