  Our measurements of variances ($\sigma_{m}^2$) in mass distributions of
fission fragments from fusion-fission reactions of light projectiles (C, O and
F) on deformed thorium targets exhibit a sharp anomalous increase with energy
near the Coulomb barrier, in contrast to the smooth variation of $\sigma_{m}^2$
for the spherical bismuth target. This departure from expectation based on a
statistical description is explained in terms of microscopic effects arising
from the orientational dependence in the case of deformed thorium targets.
