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Circum-Pacific and Caribbean Orogens |
Department of Geology and Mineralogy, University of Adelaide, Adelaide, South Australia 5001
The Cretaceous-Tertiary orogen of the Philippines forms the link between the mobile regions of Taiwan to the north and Sulawesi/West Irian to the south. The Mindanao Trench separates the south of the belt from the Philippine Sea and on the west the Manila Trench separates Luzon from the South China Sea. Relations with the late Mesozoic-Tertiary orogenic area of Borneo are more complex. The deep Sulu and Celebes Seas now intervene and the land links, the Palawan and Sulu Archipelago areas, appear to have been relatively stable in Tertiary times.
Segment: the segment has a maximum N-S length of 1600 km from north Luzon to south Mindanao. Within this region the orogenic belt (zones 3 and 4, see below) has an average width of 400 km (Fig. 1).
Zones: five zones are recognized. The orogenic belt comprises two zones: the main, Mobile Belt zone (zone 3) and, along the Pacific border, the mainly non-volcanic East outer zone (4). These zones are margined on the east by the Philippine Trench (5) and on the west by the Manila Trench (2) in the north and by the Palawan-Sulu Sea-Sulu Archipelago stable region (1) in the south.
History: where dated, the basement of the belt is Carboniferous to Permian and consists of ophiolitic rocks and flysch metamorphosed to amphibolite facies. Overlying the basement are Triassic conglomerates and Jurassic greywackes and shales, locally with spilites. These were folded at the end of the Jurassic and are overlain by a distinctive association of Cretaceous
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