Abstract: The stratigraphically lowest part of the investigated area consists of metapelites, metapsammites andmetarudites of Middle-Upper Triassic age, and is named as İkibaşlı Formation. Çiçeklikaya Formationwhich comprises of dolomitic limestones of Jura age conformably overlies İkibaşlı Formation. All  these Mesozoic aged units are tectonically overthrusted by the Muratdağı Melange with a low-angle.Muratdağı Melange composed of Neotethyan ophiolitic rocks is represented by ultramafic rocks and amelange (volcanic-sedimantary rocks) in the study area. Sub-ophiolite metamorphic rocks are tectonicallylocated between the ultramafics and melange of ophiolites of Western Anatolia in Alp-Himalaya belt.Sub-ophiolite metamorphic rocks which form under the ophiolitic rocks and have a maximum 100 meterthicknes are represented by amphibolitic rocks in the Northwestern Anatolia. Sub-ophiolite metamorphicrocks form in the period of subduction of an oceanic litosphere in the subduction zone. The ages obtainedfrom these rocks enable us to determine the age of a subduction of an oceanic litosphere and consequentlyto determine the closure age of Neotethyan Ocean. For this aim, 40Ar/39Ar age analysis was performed onhornblendes of metamorphic rocks and the plateau age of 100.7±1.3ma was determined.