TECTONIC EVOLUTION OF THE CRETACEOUS OPHIOLITIC MéLANGE (THE “ANKARA MéLANGE BELT”) DURING LATE CRETACEOUS-PRE- MIOCENE PERIOD

The so called “Ankara Mélange Belt” being a continuous deformational belt is situated on tremendous Alpine-Himalayan mountain chain between the Mesozoic-Paleogene Black Sea Magmatic Arc in north and Anatolide-Tauride Belt in south in northern Turkey, that links the Vardar Zone (Balkans) to Sevan-Akera Zone (Lesser Caucasus).

The belt is differentiated into three imbricate tectonic subbelts as i) Paleozoic metamorphics that are unconformably overlain by Triassic clastics, ii) Triassic Karakaya Complex (Mélange a blocchi calcarei) that is unconformably overlain by Liassic clastics, and iii) Cretaceous Ophiolitic Mélange (Mélange a blocchi ofiolitici).

The Cretaceous ophiolitic mélange is composed of Cretaceous ultramafics, Valanginian to Barremian pillow basalts of seamounts, Late Barremian - Early Aptian biodetrital carbonates of atolls, Oxfordinian-Turonian radiolarites and associated Cenomanian-Turonian hemi-pelagic basinal sequences, and Callovian to Aptian-Cenomanian platform carbonate blocks which all set in a highly sheared-brecciated, place to place detrital matrix. An important issue is the missing of Dogger age carbonate blocks or sequences in the Cretaceous ophiolitic mélanges.

As being a dynamic mass, the age is of the ophiolitic mélanges based on the age of constituents of the mélanges and bracketed by closely related Cretaceous basins situated structurally above. These relationships reveal an age interval of post-Albian-Aptian to Maastrichtian in northern Central Anatolia.

Collectively, the sea-floor spreading in northern Anatolia should have started prior to the evolution of the seamount (dated as Late Valanginian - Barremian) and younger than the Liassic rifting. The triggering of the carbonate platform can be the voices of initiation of subduction of the northern Neo-Tethys which is the period of Valanginian to Aptian times. The accreted dynamic mass overthrusted onto the Maastrichtian-Paleogene basinal sequences and thrusted onto Upper Miocene mudrocks with southward vergence in Ankara-Amasya region (northern central Anatolia) and back thrusted onto post-Middle Eocene – pre-Miocene sequences with northward vergence in Amasya region (east of central Anatolia) to eastern Pontides.