In the Sandikli-Afyon area, the very low-grade metamorphic Sandikli Basement Complex with elastic sediments and Late Neoproterozoic felsic igneous rocks are unconformably overlain by a cover succession with red continental elastic rocks, tholeiitic basalts and siliciclastic rocks with Early Cambrian trace fossils. Illite crystallinity studies reveal that both the basement and cover units were metamorphosed at high anchizonal to epizonal conditions (similar to 300 degrees C). Textural data together with the detailed evaluation of the P-T-b(0) grid, however, indicate that this thermal event has multiple phases. The first tectonothermal event was realized at pressures of similar to 4.2 kb on the basis of b(0)-data and resulted in development of blastomylonites. This is supported by the presence of dynamo-metamorphosed pebbles within the basal conglomerates of the Lower Paleozoic cover series. The second event is post-Ordovician-pre-Jurassic in age, occurred at lower pressures similar to 3.2 kb and produced a weakly developed cleavage in the siliciclastic rocks of the cover. The mineralogical/textural data across the basement-cover boundary therefore indicate the removal of an entire metamorphic zone and thus a metamorphic hiatus.