Littoral Sedimentary Processes — INMAN, GAYMAN and Cox 
127 
Before man changed the drainage in this area, 
most of the water that drained off of the Puu Ka 
Pele slope or that was discharged by springs 
from the ground-water body beneath the slope 
was ponded by the coastal sand dunes, forming a 
fresh to brackish marsh. Now even though the 
marsh has been drained, it seems unlikely that 
significant amounts of sediment are being sup- 
plied to the shore by streams other than the War 
mea River. The presence of large calcareous 
dunes and the dominant marine nature of the 
sediments of the Mana Coastal Plain indicate 
the importance of the transport of biogenous 
material from the sea to the land. Prograding 
of the shoreline of the Mana Coastal Plain, dur- 
ing the recent geologic past, is indicated by the 
occurrence of multiple beach ridges west of Oo- 
mano Point, and at Mana by the lithified dunes 
situated two miles inland and parallel to the 
present coastal dunes at Nohili Point. 
The carbonate content of the samples was 
high everywhere except near the Waimea River, 
where the sediments were principally terrige- 
nous. The carbonate content increased towards 
the center of the Mana Coastal Plain, attaining a 
maximum value of about 90 % at sample stations 
8 and 9 (Fig. 11, top). The median diameter of 
the samples ranged from about 250 to 800 mi- 
crons, with those near Nohili and Oomano Point 
being significantly coarser, probably as a result 
of increased wave action on the points. 
There was a pronounced bimodality in the 
size distribution, both by sieving and settling 
tube, of sediments from stations 9 and 10. This 
seems to reflect the mixing of sediments from 
the Napali-Nohili region with those from the 
south coast. The major mode occurs at 180 mi- 
crons, with a minor near 700 microns (Fig. 5). 
Microscopic examination shows the major mode 
to consist of unidentifiable fine, angular, car- 
bonate grains; the principal constituent of the 
coarse mode was foraminifera, mostly Hetero- 
stegina suborbiculcwis. In comparison, sample 
15, which consists of approximately equal por- 
tions of terrigenous and biogenous material, is 
better sorted and shows less tendency towards bi- 
modality. Sample 15, which was collected nearly 
3 miles west of Waimea River, is from a region 
of active littoral transport, where the rate of 
sorting approaches the rate of mixing of unlike 
materials. Carbonate content and size distribu- 
tion of the sediments indicate that the terrigen- 
ous material is transported along the beach west- 
ward from the mouth of the Waimea River and 
southward from the Napali Coast, and that as it 
is transported it becomes progressively more di- 
luted by biogenous material. The logarithm of 
the carbonate content is observed to increase 
linearly with distance from the Waimea River 
and from the Napali Coast (Fig. 11, bottom). 
The increase in carbonate content with dis- 
tance from the terrigenous source is indicative 
Fig. 12. Section through Mana Coastal Plain (along line shown in Fig. 11). Well numbers and well data 
taken from Macdonald, Davis, and Cox (I960). Composition of the submarine portion of the profile is 
little known and is based principally on the supposition that the section above the line of original slope of 
the dome is undifferentiated sediments, probably deposited by littoral currents at a lower sea level. 
