台湾の第三紀・第四紀の砂岩中の砕屑物の供給源の研究

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The Western Foothills and Hsuehshan Range in Taiwan are composed of clastic rocks formed mostly in shallow marine environments. An electron probe micro analyzer (EPMA) has been used to measure the ages of more than 5000 detrital monazites from 57 Tertiary and Quaternary sandstones in Taiwan, and from Recent sands which represent their probable provenance areas in East Asia. Most of the Oligocene to Pliocene sandstones from the Western Foothills have monazite age distribution patterns with peaks at ca. 150 Ma, 220-250 Ma, 430-450 Ma and 1870-1900-Ma. Comparison of the Western Foothills data with those of Recent sands has revealed there was little contribution from nearby source regions and that they were derived mainly from the Korean Peninsula with a subordinate contribution from the paleo-Yangtze River. In contrast, the Eocene to Early Oligocene sandstones from the Hsuehshan Range have a monazite age pattern with a major peak at 250 Ma and smaller peaks around 150 Ma and 450 Ma. This pattern is similar to that observed in Recent sands from the Zhu River which flows through the Guangxi and Guangdong provinces. Paleo-current directions in the Eocene to Early Oligocene sediments indicate supply from the northwest. Hence we propose that the Eocene to Early Oligocene terrane in the Hsuheshan Range was formed to the southwest of its present position and was juxtaposed against the Western Foothills by left-lateral fault movements after the Early Oligocene.
国立科学博物館の論文

台湾の第三紀・第四紀の砂岩中の砕屑物の供給源の研究

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