The Tectonic Development of Taiwan

Abstract

The metamorphosed axis of the Sakawa folded mountains is traceable into the Dainano metamorphic group. The Taiwan subgeosyncline was brought about on the continental side of this axis. In Taiwan there is no definite evidence convincing the Middle Tertiary orogeny, notwithstanding that it has previously 'been emphasized by many geologists. The change of the geosyncline which took place at that time, may be the westerly shifting of its subsiding axis. Four coal measures intercalated in the marine upper Oligocene and Miocene sediments reveal the repetition of cycles of sedimentation caused by embryonic foldings. For the provenance of exotic heavy minerals in the Neogene sediments the pre-Taiwan dome in the foreland which belongs to the Akiyoshi folded mountains is suggested. The geosyncline was strongly deformed by the Taiwan orogeny in the Plio-Pleistocene epoch and its typical orogenic sediment is the Shokkozan conglomerate. The mountain structure introduced thereby is analysed into the Dainano, Urai and West Taiwan zones with the Kiirun imbricated subzone and the Towen undulated subzone in the northern part of the last zone and their characteristics are pointed out. In addition, brief notes are given on the Daito coastal range and dependent isles later history of Taiwan is discussed in some length.