Foraminiferal analyses of Cenozoic strata of Central Valley, Luzon, and southern Iloilo, Panay, indicate a general planktonic zonation for the Middle and Later Cenozoic which is similar to that recognized in equivalent marine strata of other tropical areas of the world.

There is generally parallel basinal development in Central Valley, Luzon and Iloilo, Panay, beginning in the Late 0ligocene·Early Miocene interval. The cycle commenced with shelf-type conditions and orbitoidal facies giving way upward and with time to increasingly deeper-water facies of the bathyal zone. Maximum water depths of at least 1,000-2,000 meters were attained during the Miocene as indicated by Nonion barleeanus, Nonion pompiliodes, Pullenio bulloides, Osonguloxria. bengalenais, Loticarinina pauperata, and others. The parallel history in the two areas stops in the Late Miocene when Central·water paralic facies. In Iloilo, deep basinal conditions prevailed into the Middle Pliocene before basin-filling occured.

The more complete planktonic sequence is that of Iloilo. Late Oligocene time is suggested by Globigerina. concinna oiperoenais in at least on part of the basin. Early Miocene time (Aquitanian) is represented by a lower Globigerina dissimilis zone and an upper Globoquadrina tripartite rohri zone. Middle Miocene time (Burdigalian) is indicated by a lower Globorotaliu, fohsi fohai population giving way upsection to first left-coiling populations of Globarotalia menordii pmemenardii and then to right-coiling populations of the same species. From bottom to top, Upper Miocene zones include a basal Globoquadrtno demacens cdoemz. zone, ¤ Glaboquuvdrinu. altispira althpirn. zone (top of occurrence), a Globigerina. nepenthes zone (top of occurrence), and at the top a Globoquadrina altalspim globasu.-Globoquadrinm dehiacens dehiaeenc zone. Lower Pliocene populations are characterized by Sphaeroidinella dehiseens dehiscena and Globigerina egyeri (dextral). Middle Pliocene populations lack these but include an abundance of Globorotalia truncatulinoides and Globorotalia. menardii. Pulleniatina obliquiloculata is common to abundant in the Middle and Lower Pliocene section and rare in the uppermost Miocene. It is dominantly right coiling in the
middle and most of the Lower Pliocene, left-coiling at the base of the Pliocene, right-coiling and rare in the uppermost Miocene, and mostly left-coiling and very rare below.

Upper Pliocene and Pleistocene beds lack definitive planktonic zonation, probably because of the filling of the basins and the advent of paralic facies in the Pleistocene.