Study of Anisotropy of Magnetic Susceptibility on Central Chimei Fault, Coastal Range of Eastern Taiwan

Abstract:

The Chimei fault is the only major reverse fault across the entire Coastal Range and is also a typical lithology-contrast fault thrusting the volcanic Tuluanshan Formation of Miocene over the sedimentary Paliwan Formation of Pleistocene. To investigate the deformation pattern across the Chimei fault more precisely, we analyzed oriented coring samples of mudstone across the fault zone, damage zone, fold zone and wall rocks along the Hsiukuluan River via anisotropy of magnetic susceptibility (AMS).

Prolate (cigar-shaped) and oblate (disc-shaped) ellipsoids appear together at fault zone, damage zone and fold zone, suggesting that strong variation of deformation and lithology in each zone of the Chimei fault. Previous study pointed out that oblate ellipsoid usually appears in the footwall, further indicating that the Chimei fault behaves differently from regular detachment faults. It strongly speculates although the central Chimei fault displays N-S shortening, the deformation is not strong enough to develop penetrative oblate fabric, even in the main fault zone of the Chimei fault. Further studies will be rnrformation is not sobear theequired to identify the magnetic carriers and grain size to improve current concept.

Keywords : Anisotropy of Magnetic Susceptibility, Coastal Range, Chimei Fault, Taiwan