Palaeomagnetism and magnetic anisotropy of proterozoic banded-iron formations and iron ores of the Hamersley Basin, Western Australia

Abstract

The deflection of post-folding remanence towards the bedding plane by high magnetic anisotropy can produce an apparent synfolding signature, with best agreement between directions from different fold limbs after partial unfolding. The effect of magnetic anisotropy of banded-iron formations on measured remanence inclinations and inferred palaeolatitudes can lead to large errors in calculated palaeopoles for intermediate to moderately high palaeolatitudes but is minor for low palaeolatitudes. Anisotropy also causes cones of confidence to be underestimated, due to compression of the range of inclinations. Therefore high anisotropy can not only bias estimated palaeofield directions and cause underestimation of errors, but can also mislead interpretation of the relative timing of remanence acquisition.