The LiuchiuHsuIsland offshore SW Taiwan:the Mud Volcano or the Compressing Tectonic Diapiric Anticline.
Liang Shen-hsiung
Abstract
The Liuchiu Hsu island, which is about 12 km off the southwestern coast of Taiwan, is located near the KaopingSubmarineCanyon. Its northeast-southwest major axis is about 5 km, and the maximum width in the northwest-southeast direction is 3 km. The shape of the Liuchiu Hsu island is like a peanut and the area is about 10 km2 above sea level. There are two major rock formations in the island. One is large amounts of mudstones and siltstones, which was folded during the Early Pliocene; another is composed of Pliocene gray mudstones that is unconformably capped by a 4-10 m thickness of Pleistocene reef limestone. Ongoing debate about whether the origin of the Liuchiu Hsu island is mud volcanoes related or compressing tectonic related has been discussed by previous researchers.
Chow et al. (2001) based 3.5kHz, UNIBOOM and conventional seismic data. They detected some structural and sediment features such as debris flow, channel cuts, eroded truncation, shallow faults and four represent sedimentary sequence boundaries of Pleistocene near the Liuchiu Hsu island. By these data, they thought that the Liuchiu Hsu island is a mud volcano, because the mud deposited speedy and the Kaoping paleo-canyon eroded the overlying sediment away to release the overlying pressure.
Lacombe et al. (2004) used the fault slip data, the calcite twin data and the sedimentary strata, and found that two main periods of the paleostress directions were identified: an extension with no dominated stress orientation, and a NW-SE compression measured similar to the Plio-Quaternatry stress in Taiwan, and concluded that the anticlines of SW Taiwan extend into the sea.
They synthesized the above information and hypothesized the Liuchiu Hsu island was a compressing tectonic diapiric anticline related to the Plio-Pleistocene tectonic history. There were growing coral on top of the mud diapir, finally, forming the landscape we see today.
Refernce
Angelier J., Tectonic analysis of fault slip data sets, Journal of Geophysical Research, B 89 (7), 1984, 5835-5848
(Abstract)(Full text)
Chow J., Lee J.S., Liu J.S., Lee B.D., and Watkins J.S., A submarine canyon as the cause of a mud volcano: Liuchieuyu island in Taiwan, Marine Geology 176, 2001, 55-63
Lacombe O., Angelier J., Mouthereau F., Chu H.T., Deffontaines B., Lee J.C., Rocher M., Chen R.F., Siame L., The Liuchiu hsu island offshore SW Taiwan: tectonic versus diapiric anticline development and comparisons with onshore structures, Comptes Rendus Geoscience 336, 2004, 815-825