῏῍ΐῐῌ (48), pp. 177ῌ199, 2012 ῒ 3 ῎ 28 ῑ Mem. Natl. Mus. Nat. Sci., Tokyo, (48), pp. 177ῌ199, March28, 2012 Provenance Study of Jurassic to Early Cretaceous Sandstones from the Palawan Microcontinental Block, Philippines Kazumi Yokoyama1, ῍, Yukuyasu Tsutsumi1, Tomoki Kase1, Karlo L. Quean˜o 2 and Aguilar Yolanda M.2 1 Department of Geology, National Museum of Nature and Science, Tokyo, 4ῌ1ῌ1 Amakubo, Tsukuba, Ibaraki 305ῌ0005, Japan 2 Mines and Geosciences Bureau, Diliman, Quezon City, Philippines ῍ E-mail:
[email protected] Abstract. The Palawan microcontinental block in the Philippines was separated from the southwestern coast of the Asian continent (i.e. southwestern Taiwan) during the opening of the South China Sea in the Oligocene to Miocene times. In this paper, provenances of the detrital grains in the Jurassic to Early Cretaceous sandstones from the Palawan block were studied to determine whether they were derived from the Asian continent. Age distributions of detrital monazites in the sandstones from the Busuanga, Mindoro, and Panay islands are essentially bimodal with peaks at 140ῌ260 Ma and 1800ῌ2000 Ma. Such a pattern is not recognized from the region of assumed origin before the opening of the South China Sea nor from the Indochina Peninsula. A similar bimodal pattern is observed on the Korean Peninsula, in coastal areas of the Shangdong Peninsula, and in Zhejiang Province in China. These areas are located at the marginal East China Sea. Hence, it is concluded that the Jurassic to Early Cretaceous sandstones of the Palawan microcontinent were parentally deposited on the eastern side of present-day Taiwan.