434 
PACIFIC SCIENCE, Vol. XXII, October 1968 
LEGEND FOR TA'U ISLAND 
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Qb 
CALCAREOUS SEDIMENTS 
Modern beaches (Qb) composed of unconsolidated fragments of marine 
organisms. Beaehrock is frequently present. 
NONCALCAREOUS SEDIMENTS 
Alluvium (Qa), including talus, landslide debris at the base of cliffs, 
and stream deposits. In areas behind constructional benches marshes (Qn) 
sometimes occur. 
FITI IUTA FORMATION 
Lava flows (Qfl) of basalt and olivine basalt forming the bench at 
Fitiiuta. An associated cinder cone (Qfc) is mapped separately. 
Qft 
FALEASAO FORMATION 
Undifferentiated tuff complex (Qft) of palagonitized vitrie-erystal 
lapilli tuff, breccia, and occasional horizontal lava flow's from at 
least three main cones centered at Faleasao, To’a, and Fa’asemene Coves. 
MAJOR EROS ION AL UNCONFORMITY 
Qlc 
Qlp 
LUATE l 
. E 
FO 
RMATION 
Thin pahoehoe flows (Qlp) of olivine basalt and 
pierite-basalt have built Luatele shield on the 
northeastern portion of the island. The depres- 
sion was partly filled with ponded lavas (Qlc) . 
TUN OA FORMATION 
Lava flows (Qte) of basalt and olivine basalt 
have built Tunoa shield on the northwestern 
portion of the island. The depression formed 
by collapse of this shield was partly filled 
with volcanic deposits (Qte) of red vitric- 
crystal ash, lapilli tuff, and olivine basalt 
lavas, some of which contain dunite xenoliths. 
Associated cinder cones (Qtcc) are mapped sep- 
arately where possible. 
LATA FORMATION 
Lata shield consists of pre-caldera, post-caldera, and 
intra-caldera deposits. The pre-caldera member (Tie) 
consists of lava flows of olivine basalt, pierite-basalt, 
basalt, feldepar-phyric basalt , and hawaiite with occa- 
sional beds of tuff. Most of these rocks have been mantled 
by post-caldera deposits (Qle) of olivine basalt, pierite- 
basalt, basalt , and hawaiite which were' erupted from cones 
on the flanks of Lata shield. Where possible, late cinder 
cones (Qlec) and Recent lava flows have been mapped separ- 
ately. Usually the pre-caldera lavas and the post-caldera 
lavas cannot be separated and are mapped together as extra- 
caldera rocks (Qle) except in a few areas where it appears 
likely that pre-caldera rocks (Tie) are exposed. The intra- 
caldera member (Qli) consists mainly of dense flows of 
olivine basalt, pierite-basalt, basalt, and hawaiite with 
numerous thin beds of vitric -crystal ash. An intra-ealdera 
cinder cone (Qlic) and its associated lava flows (Qlil) of 
basalt are mapped separately. A dike complex intruded pre- 
calderaC?) rocks at Laufuti. 
PLIOCENE PLEISTOCENE RECENT 
