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PACIFIC SCIENCE, Vol. XVII, January 1963 
Fig. 5. Size distribution curves for sand samples 9 and 15, showing comparison 
between settling tube and sieve analysis. Grain size distribution curves are also 
presented for the carbonate and noncarbonate fractions, which make up 53% 
and 47%, respectively, of sample 15. The size distribution curves for sample 9 
(89% calcium carbonate) show a marked bimodal distribution, which is not 
typical of most highly calcareous samples of Kauai. In this case, the bimodal 
distribution reflects the differences between the coarse carbonate grains arriving 
from the north and the finer, but more abundant, carbonate grains from the east. 
coarser sieve fraction than their settling velocity 
would indicate. Comparisons between sieve and 
settling tube analyses are shown in Figure 5. 
The most common beach sediment had a me- 
dian diameter of about 350 microns, while the 
median size of all samples ranged from 140 to 
1400 microns. Although the size distributions 
of the samples from the windward and leeward 
coasts as a group were not markedly different, 
smaller coastal segments did show significant 
longshore trends of increasing or decreasing 
grain size. There is a tendency towards bimodal- 
ity in sediment size distribution, especially 
where mixing of sediment from different trans- 
port directions occurs southeast of Nohili Point 
(Sample 9, Fig. 5). Also, the beach face sedi- 
ments from Kauai, which had an average phi 
deviation measure of about 0.5, are less well 
sorted on the average than those from typically 
continental beaches. Well-sorted sand of similar 
size from continental beaches would have a phi 
deviation measure of about 0.3 (Inman, 1949, 
1953 ). The more frequent interruption of lit- 
toral drift by points and headlands, and the con- 
tinuous addition of a heterogeneous assortment 
of material from reefs and from offshore, prob- 
ably account for this difference in sorting. 
The slope of the beach face increases with 
increasing sand size and with decreasing wave 
height and intensity. Beaches like those at Ka 
paa, which are protected by broad fringing reefs 
from the direct attack of large breakers, were 
consistently steeper than more exposed beaches. 
Also, beaches inside protected bays (as Station 
30, Hanapepe; Table 2 ) were steeper than those 
exposed to- the open sea (as Stations 1-7 at 
Nohili, and Station 86 at Flanakapiai ) . The re- 
lation between beach slope and sand size for 
various type beaches is given in Figure 6. 
Biological Analysis 
The only completely identifiable biogenous 
components present in significant quantities in 
the sands were the benthic foraminifera Hetero- 
stegina sub orbicularis and Amphistegina mada- 
gascariensis . Other positively recognizable com- 
ponents, including other foraminifera, echinoid 
spines, sponge spicules, gastropod shells and 
