438 
PACIFIC SCIENCE, Vol. XXII, October 1968 
which is approximately 200 feet in diameter 
and about 200 feet deep. Exposed in the walls 
of this pit crater are thin-bedded shield-buliding 
pahoehoe flows. 
Luatele flows are also exposed in the old sea 
cliff behind Fitiiuta Village. In the cliff along 
the north coast of the island the contact between 
the Luatele lavas and those from the Lata shield 
was not found because of poor exposures. How- 
ever, the topography and outcrops of the char- 
acteristic lavas inland from the cliff indicate 
the approximate location of the contact, as does 
the composition of talus boulders at the base of 
the cliff. 
The western boundary of the Luatele lavas 
has been masked by the eruption of a post- 
caldera cone, Sa’umane Crater, located near the 
edge of the sea cliff. Oceanite occurs at the 
vent, and the flow itself is an olivine-rich, 
vesicular basalt. Flows from this cone, as well 
as from the Luatele shield, all seem to predate 
the sea cliff. Nearby, however, a few of the 
youngest Lata lavas have flowed over the sea 
cliff near Saua Stream. 
faleasao formation: The area on the 
northwest corner of the island, including Fa- 
leasao Village and extending east beyond Si’u- 
lagi Point to Tulatula, is a complex of two or 
three tuff cones. One of these cones is centered 
at Faleasao, another at To’a Cove, and probably 
a third, smaller one at Fa’asemene Cove. Coral 
fragments included in the tuff indicate that the 
eruptions came from vents cutting through a 
contemporary or relict fringing coral reef; they 
were therefore probably formed near sea level. 
The cones grew above sea level and covered the 
old sea cliff. Pisolites on the surface of the beds 
on the south flank of the Faleasao cone, at the 
northern end of Ta’u Village, indicate that rain 
accompanied the eruption and are evidence for 
subaerial deposition. 
At Tulatula, the Faleasao tuff appears to have 
buried a sea stack of thin-bedded pahoehoe 
basalt flows that are unconformably overlain by 
a thicker flow of oceanite. These lavas most 
likely are part of the Tunoa shield. Offshore 
bathymetry suggests that the base of the tuff 
complex is about 600 feet below sea level, in- 
dicating that the Faleasao Formation is at least 
1,100 feet thick. 
The rock making up most of the formation is 
a vitric-crystal lapilli tuff of basaltic composi- 
tion. Most of the lapilli are accidental, but some 
are accessory. Blocks and bombs also occur in 
the tuff, particularly in the area around Fa’a- 
samene Cove, where the blocks increase both 
in number and size, sometimes measuring over 
2 feet in diameter. Along the northeast part of 
that cove, oceanite boulders more than 15 feet 
in diameter are found, but they are probably 
remnants of a small flow ponded within the 
Faleasao tuff cone. 
Although magmatic bombs occur in many 
different areas, they are particularly abundant in 
the cliff behind Faleasao Village. Bombs up to 
4 inches in diameter and associated bomb sags 
are exposed in thin beds, 0.5 inch to 1 foot 
thick, in the southeast portion of the inner crater 
wall. In this same area, the pulsating activity 
which built the cone is recorded in rhythmically 
graded beds, which are approximately 2 feet 
thick. At least four or five of these beds are 
exposed; each unit grades from lapilli tuff into 
fine-grained tuff. Overlying this series is a bed 
of volcanic breccia approximately 3 feet thick. 
Breccia occurs elsewhere in the formation and 
is especially abundant around Fa’asamene Cove. 
The point between Fa’asamene and To’a coves 
contains an exposure of the crest of a palago- 
nitized tuff cone overlain by breccia with an un- 
palagonitized, black ash matrix. The breccia is 
mostly accidental basalt and some picritic basalt. 
The blocks usually range in size from about 1 to 
4 inches, although some are as large as 6 feet in 
diameter. Lapilli of dunite, coral, and palagonit- 
ized tuff are included within the black ash ma- 
trix, and some of the blocks of basalt contain 
dunite xenoliths. 
Dunite xenoliths up to 2 inches in diameter 
are found in the lava blocks included in the 
breccia near Fa’asemene Cove. Dunite is also 
found as separate inclusions ranging from 0.1 
inch to more than 6 inches in diameter. These 
nodules of dunite are extremely abundant on 
the westernmost part of the cone at Si’ua’i 
Point. The dunite is essentially 100 per cent 
olivine, though a few augite crystals were found. 
Coral blocks up to 4 inches in diameter were 
also found at Si’ua’i Point. Smaller fragments 
less than 1 inch across were found in the cliff 
