 BackResearch Article ScienceAsia 28 (2002) : 277-290 |doi: 10.2306/scienceasia1513-1874.2002.28.277
Magnetic Characterization of the Thung-Yai Redbed of Nakhon Si Thammarat Province, Southern Thailand, and Magnetic Relationship with the Khorat RedbedTripob Bhongsuwan* and Pornpan Ponathong
Department of Physics, Faculty of Science, Prince of Songkla University, Hatyai 90112, Thailand. Received 26 Jul 2001, Accepted 6 Feb 2002
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SI), natural remanent magnetization (3.19-13.59 mA/m) and Koenigsberger ratio (0.96-3.65) of the specimens are similar to those of the Khorat redbeds. Low anisotropy degree Pj of 1 - 7 % indicates a low degree of deformation in the Thung-Yai redbed. Distribution of the principal axes of susceptibility indicates an imbrication of the minimum axes (K3) toward the West which is interpreted as the palaeo-current direction during deposition of sediments. There are probably gravitational and hydrodynamic forces of flowing water that affect the Thung-Yai redbed at the time of deposition. Analyses of magnetic data and fluorescent X-ray images indicate that magnetite and haematite are the predominant magnetic minerals in the Thung-Yai redbed. This shows a non-marine environment during sedimentation. Remanent magnetization derived from a high temperature range of 530 - 630 oC directed at Dec/Inc = 32.6o/18.8o is considered to be primary remanent magnetization and its pole position is at Plat/Plon = 57.8oN/ 184.6oE. This pole overlaps well with the pole position derived from the Khorat redbeds (Plat/Plon = 60.7oN/181.0oE). This indicates that the Shan-Thai block, the parent block of southern Thailand and Indochina block, the parent block of the Khorat plateau, have not moved with reference to each other since the Upper Jurassic – Lower Cretaceous
