156 
drilled on the Ewa Coastal Plain are not the 
only holes that have been drilled on that plain. 
Hundreds of wells have been drilled from 
Barber’s Point to Honolulu and from the 
mountains to the sea during the past 40 years 
(Stearns and Vaksvik, 1935, 1938). However, 
no samples were saved from these holes. Logs 
of these wells are frequently ambiguous as to 
terminology; "coral” and "limestone” are used 
interchangeably, and it is suspected that any 
white rock penetrated by the drill was logged 
as "coral.” 
Using recovered cores from Ewa Nos. 1 and 
2, however, it has been possible to go back 
to these earlier logs and reinterpret them. In 
this manner a great deal of additional informa- 
tion was obtained that could be used to extrap- 
olate the data from the Ewa holes (Figs. 2 
and 3). 
Mr. William Ebersole assisted in the project 
The holes were drilled by Layne International 
Company of Honolulu. 
LITHOLOGIC TYPES 
The sedimentary rock in the two Ewa cores 
consists mainly of various types of reef lime- 
stone alternating with shallow-water muds. A 
few soils, a layer of beach rock, two beds of 
lignite, basaltic sands, and stream conglomerates 
were encountered. The igneous rock recovered 
in the lower portion of each core consists of 
alternate flows of pahoehoe and aa basalt. 
Lithologic terms used throughout the following 
discussion are defined below: 
Reef limestone. A sedimentary rock con- 
sisting of the remains of various corals, mainly 
Porites, calcareous algae, molluscs, etc., essenti- 
ally in position of growth. Much of the original 
skeletal material has been replaced by secon- 
dary calcite and/or dolomite. 
Mud. A marine or fresh water sediment con- 
sisting of particle diameters mainly in the silt 
and clay size range, i.e., 1/16 mm to about 
1/1000 mm, and composed of various detrital 
minerals resulting from terrestrial weathering. 
Marine shells may be present. The various 
types of muds are described in terms of their 
colors; the muds in the Ewa cores owe their 
colors to the following constituents: (a) oxides 
of iron and aluminum (brown mud) ; (b) iron 
PACIFIC SCIENCE, Voi. XXI, April 1967 
sulfides and organic detritus (black mud) ; (c) 
calcium carbonate particles mixed with brown 
or black mud (gray mud) ; (d) clay size 
particles of calcium carbonate presumably reef 
detritus (white mud) ; (e) clay minerals and 
ferrous iron (green mud). 
Beach rock. A sedimentary rock consisting of 
calcareous beach sand cemented by calcium 
carbonate. Beach rock is commonly found form- 
ing within the beaches of tropical islands and 
owes its origin to the seepage of carbonate-rich 
ground waters through a beach composed of 
calcium carbonate particles. Beach rock is 
formed only at or within the tidal range and 
positively indicates a former shore line. 
Reef breccia. A sedimentary rock composed 
of the angular fragments of an organic reef. 
The broken fragments may be y 2 -4 inches in 
diameter and are commonly mixed with sand 
and silt-size reef debris. 
Lignite. Fossil plant remains altered by pres- 
sure to a highly friable, soft, black sedimentary 
rock. A low grade of coal. 
Conglomerate. A sedimentary rock composed 
of rounded cobbles and pebbles intermixed 
with finer material. 
Clinker. Rough, spinose, vesicular fragments j 
of lava produced by lava flow. 
Pahoehoe basalt. Lava with a smooth or ropy j 
surface spread chiefly through tubes and char- ; 
acterized by round vesicles. 
Aa basalt . A lava flow with a rough clinkery 
surface and base. Deflated and stretched vesicles 
characterize the solid part of the flow. 
Marl. A calcareous clay. 
Soil. The term is used in a general way to i 
mean regolith on the basalt and any sediment 
altered by weathering. 
Cobbles, pebbles, gravel, sand, silt, clay. The 
usage herein follows the usual dictionary defini- 
tions. 
MEGASCOPIC DESCRIPTION OF CORES 
Ewa No. 1 (Table 1) 
The drilling site for this hole was located as 
far seaward on the Ewa Coastal Plain as it was 
feasible to drill, within 200 yards of the sea 
on the 158th meridian on the eastern end of 
the property of the U. S. Coast and Geodetic 
Station, 91-270 Fort Weaver Road, Ewa Beach, 
