Melanges are usually dated from the ages of contained blocks and of the oldest unconformably overlying cover rocks. Anomalies associated with this approach are illustrated in this study of the principal melange belts developed in Anatolia.
The Karakaya Melange belt of supposed Middle Triassic inception and the Ophiolitic Melange belt of supposed Late Cretaceous age are readily distinguished in western Turkey but their outcrops converge eastwards, the two belts merging in Central Anatolia and becoming intermingled further east, near Sivas, where the ages and natures of the melange belts are problematic. Thus parts of the melange attributed to the Karakaya belt contain blocks of younger limestone (Jurassic to Early Cretaceous or even younger), whereas outcrops attributed to the Ophiolitic Melange include blocks of clastics of Late Palaeocene-Early Eocene or even Mio-Pliocene age. This situation confers apparently 'younger' ages of formation on these melanges. It is suggested that such anomalies result from contamination by younger blocks as a result of local remobilization of the melanges during subsequent tectonic disturbances.
A north-south oriented area, 45 km long and 20 km wide, crossing the complex melange zone east of Sivas, has been mapped at a 1:25 000 scale and provides critical evidence on this question. It appears that the Karakaya Melange (or its equivalent) may have been remobilized at least four times and the Ophiolitic Melange at least three times since their inception. During each subsequent tectonic event the melanges have incorporated some parts of the younger deposits which formed on top of them in the intervening geological periods.