Reconnaissance by Submarine — Brock and Chamberlain 
381 
Fig. 3c. Bathymetric profiles Nos. 11-15. See 
Figure 1 for locations. 
from one terrace to another, and the escarpment 
is almost completely hurried by nearshore sand 
for almost one-half its length — from Makua 
Point to Kepuhi Point. 
Figure 2 shows the relationship of this deeper 
escarpment to the upper terrace levels and gen- 
erally to the land topography. Figure 9 shows 
a detailed picture at a point slightly north of 
Makua Valley. Generally this escarpment be- 
tween the Lualualei and Mamala shelves is 
much more pronounced in the area north of 
Makua Valley. In places it is perfectly vertical 
for over 30 meters with caverns and indenta- 
tions in the lower levels and in some localities 
large boulders at the base. The amount of sand 
in the offshore zone increases to the south (as 
explained in the section on Littoral Processes 
below), and this increase in offshore sand par- 
tially masks the base of this escarpment and, 
far to the south near Kepuhi Point, completely 
obliterates it. Starting at about Makua Valley, 
large spillways or canyons cut through the 
escarpment and, together with the sand spilling 
over the rim and fragments from the escarpment 
itself, form immense talus slopes (Fig. 9). On 
most of the dives directly to 180 meters the 
"Asherah” alighted on a 10°— 15° talus slope 
which dropped off seaward into darkness and 
extended upward and shoreward to the base of 
steep cliffs or over broken outcrops of rock to 
the Mamala Shelf. 
In the area of investigation it would be al- 
most impossible to fix the depth of the inshore 
edge of the Lualualei Shelf by means of echo 
soundings : the sand and talus deposits are 
probably tens of feet in thickness and com- 
pletely bury the inner portion of the shelf. Just 
south of Kaena Point, where the base of the 
escarpment is covered with large boulders, the 
depth is approximately 186 meters. These 
boulders most probably are the remnants of a 
boulder beach; together with the near vertical 
escarpment above them they possibly represent 
the strand line and sea cliffs for a very pro- 
longed stand of the sea. The age of the Lualua- 
lei Shelf is not known, but its possibly warped 
and titled surface (Ruhe, 1964) and the 
recovery from it of a possible Miocene fauna 
(Menard, Allison, and Durham, 1962) would 
indicate mid-Tertiary. Irrespective of the ab- 
solute age, a long period of stability of the sea 
level is indicated by the massive nature of the 
escarpment observed from the "Asherah.” A 
continuation of this escarpment can be traced 
around most of western and southern Oahu. 
The upper edge of the escarpment described 
above terminated abruptly in a nearly horizontal 
marine terrace. The seaward or deeper edge of 
this terrace generally was encountered at depths 
of about 120 meters, but ranging from approxi- 
mately 100 to 140 meters in depth. Landward 
the terrace continued for hundreds of meters, 
finally terminating against a very broken line 
of irregular outcrops. Figure 8 is a representa- 
tion of this intermediate terrace (here referred 
to as the Mamala Shelf) at a depth of about 
90 meters. The nature of the outcrops defining 
its inner edge is shown as well as some of the 
surface features of the shelf. The outcrops 
themselves were very interesting as many had 
large caves in their seaward sides and were 3 to 
6 meters in height and perhaps twice that in 
diameter. A definite delineation of these out- 
crops, generally parallel to the shoreline, could 
be seen. A representation of this delineation is 
attempted in Figure 8. 
It was possible to trace the Mamala Shelf 
landward in some areas to depths of less than 
