Detrital white mica from two distinct Cretaceous stratigraphic levels and tectonic settings within the Apuseni Mountains (Mts.) and northernmost South Carpathians was dated using the single-grain ⁴⁰Ar/³⁹Ar technique in order to monitor the geodynamic evolution of this peculiar segment of the Cretaceous-aged Carpathian orogen. ⁴⁰Ar/³⁹Ar mica ages of a Lower Cretaceous synorogenic flysch succession in the Apuseni Mts. indicate the preservation of Early Variscan and Late Variscan orogenic metamorphic crust in the source region. By contrast, only a low percentage of Variscan micas have been detected in the post-orogenic Late Cretaceous Gosau-type Vlădeasa collapse basin of the Northern Apuseni Mts., which postdates the emplacement of the Mureş ophiolite belt and the Early to early Late Cretaceous formation of the low-grade metamorphic orogenic wedge. There, the studied micas are dominantly of early Late Cretaceous age and argue for the erosion of a medium-grade early Alpine metamorphic unit, which is not exposed in the surroundings of the present-day Apuseni Mts. Consequently, the Apuseni Mts. must have been either disrupted from such a source area and shifted along major strike-slip faults to the present position, or the source is now hidden. In contrast, the Late Cretaceous Gosau-type Rusca Montană basin of the South Carpathians comprises dominantly Variscan and a few Triassic detrital mica grains, consistent with Variscan and subordinate Triassic ages of the underlying and surrounding basement exposed in the Supra-Getic/Getic nappes.