The basin began to sink in the Middle Miocene, which is
indicated by gradual change of the deposition from claystones,
silty claystones and fine sandstones (in the upper part of the
Fat’ha Formation) to the sedimentation of clastics (mainly
sandstones of the Injana Formation). This sinking continued
until Pliocene, resulting in the deposition of coarse clastics of
Mukdadiya (Lower Bakhtiari Formation). Then the basin was
filled by coarser clastics of Bai Hassan (Upper Bakhtiari
Formation). These materials were derived from the rising
Zagros basin (Sissakian and Youkhana, 1978).