How was Puli basin group created ?

Ching-Chia Huang

Abstract

The Puli basin was located at southern Hsuehshan range, this is one of the inter-mountain basin group.The basin group is NNE-trending, north to Peikang river, south to Jhuoshuei river, from north to south is Puli, Yuchih, sun-moon lake, Tousher and Tungkuei. There are 30 km in length, the Puli basin has an area of 42km2, whereas the Tungkuei basin is less than 1 km2. The created way of this basin group is one question of Taiwan geology until now.

According to previous studies in this area, there are four main inference:

(1) Downwarp and river erosion.(Hayasaka,1984, Tomita,1951) (2)Piggy back basin from orogeny.(Ori and Friend,1984, Muller et al.,2002) (3)Created by transtension.(Biq,1989) (4)There is a detachment beneath the basin group.(Chen et al, 2001)

Nevertheless, according to what the latter author depicted in a profile from Puli to Tungkuei, there is not a huge syncline but NNE-trending thrust faults and folds.In addition, except Puli basin is not sure, others are closed basin, for these reasons, Puli basin was not created from warping and river erosion. The Hsuehshan range was uplifted through late-pliocene, and the Chuchih fault was at least acted in 2.5Ma, the western foothill was uplifted in 1 Ma.Therefore, if Puli basin is a piggy basin with thrust faults action, the sediments at the bottom of basin should not so young as mid-pleistocene.

We can’t exclude the other two versions, however, we need more geological or geophysical research to understand the definite process about how was Puli basin created.

Reference

陳炳誠(2002) 埔里與魚池盆地之沉積與新構造研究。台灣大學碩士論文。

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Biq, C. C. (1989) The Yushan-Hsuehshan Megashear zone in Taiwan. Pro. Geol. Soc. China, Vol.32, NO.1 ,7-20

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Chen, W. S., Huang, B. S., Chen, Y. G., Lee, Y. H., Yang, C. N., Lo, C. H., Chang, H. C., Sung, Q. C.,Huang,N. W., Lin, C. C. Sung, S. H., Lee, K. J.(2001)1999 Chi-Chi Earthquake:A Case Study on the Role of Thrust-Ramp Structures for Generating Earthquakes. Bulletin of the Seismological Society of America, NO.91,5,pp. 986-994.

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