The temporal evolution of the Zagros Simply Folded Belt is constrained by a magnetostratigraphic sequence containing a progressive unconformity on the southern limb of the Kuh-e Ghol Ghol anticline, in the Central Fars. The investigated similar to 1400m thick sequence exposes a regressive megacycle containing, from bottom to top, open and shallow marine marls and sandy limestones, fine- to coarse-grained fluvial deposits and alluvial conglomerates. Correlating the magnetostratigraphic section with the geomagnetic polarity time scale constrains the transition from marine to fluvial sediment deposition at similar to 6Ma. This transition was accompanied by a change in the accumulation rate from similar to 15cm/ka to similar to 40cm/ka, as measured on lithified sediments. Alluvial river deposits first occurred at similar to 3.2Ma. The Kuh-e Ghol Ghol anticline began to grow at similar to 3.8Ma, witnessing fastest limb rotation rates of 40 degrees/Ma at similar to 3.3Ma. Reporting magnetostratigraphic sections and ages of growth strata on a map of NE Fars reveal an similar to 1cm/a, southwestward migration rate of the deformation front during the middle and late Miocene.