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Features resulting from the interplay of arc magmatism, ophiolite accretion, ocean basin closure and other subsequent tectonic processes are preserved in the Philippine island arc system. Subduction of ocean floor along the trenches surrounding the Philippines is a major factor in shaping the geologic history of this island arc system. Stress-strain relationships, as manifest in both the regional and local setting of the archipelago, are derived from the interaction of at least four major plates: Sundaland, Philippine Mobile Belt, Philippine Sea and, to a certain extent, the Indo-Australian plate. Collision zones in this island arc system are characterized by the involvement of oceanic bathymetric highs (seamounts, spreading ridge, submerged continental fragment). A major strike-slip fault, the Philippine Fault Zone, with compressional and extensional components, traverses the whole archipelago where all excess stress not accommodated by the surrounding trenches is taken up. Tholeiitic through adakitic to calc-alkaline rock suites characterize the different magmatic arcs. Exposed oceanic lithospheric fragments exhibit transitional mid-ocean ridge, back arc basin to island arc geochemical characteristics. The observed crustal thickness in the Philippines resulted from combined magmatic (volcanism) and amagmatic (ophiolite accretion) processes, with the former being the dominant factor.

Alternating chert-clastic sequences juxtaposed with limestone blocks, which are

The North Palawan Block is regarded as the southernmost continuation of a Late Mesozoic accretionary complex, which developed along the length of the East Asian margin. It records a long (up to ~ 100 My) period of pelagic deposition on an oceanic plate from Late Permian to Late Jurassic when subduction resulting in the disappearance of the plate by the Early Cretaceous began. Subduction-accretion resulted in the development of three lithotectonic belts. From thirteen localities within these belts, radiolarian investigations yielded 173 species belonging to 92 genera and 45 families. Most of the samples contain Middle to Upper Triassic faunas. Several sections containing upper Permian, Lower Jurassic, and Middle Jurassic assemblages were also found. The presence of benthonic and planktonic foraminifers at some localities indicates that portions of the Liminangcong Formation were deposited in environments above the carbonate compensation depth (CCD). Manganese deposits found in some areas (e.g. Busuanga and Dabatonay) suggest that parts of the depositional area experienced a very low average sedimentation rate. Examination of the North Palawan accretionary complex reveals the ghosted history of the Izanagi Plate and constrains the timing of subduction beneath the eastern margin of Asia.Cenozoic geology of the North Palawan Block. The Calamian Island Group is an integral part of this block and has been the subject of such investigations (Isozaki et al

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