Abstract: The Ophiolites, which includes green and blueschists cover large areas in the Middle Sakarya Region. Theformation of the ophiolites, the age of the green-blueschists and their age of emplacement were established with somecertainity. These findings have vontributed to the understanding of the general geology of the area in the following ways:Extensive spilitic volcanism occured between Late Permian-Triassic times. Within this time period the area waseffected by tensional forces. Limestones which had been deposited on the shallower parts of the area were faulted andgenerated different size of blocks. These limestone blocks were mixed with the products of the spilitic volcanism.Serpantinized ultrabasic rocks; gabbros which were out by diabases; red pelagic ciaystones, radiolarites which wereformed in an already existed ocean basin during Triassic time were later emplaced over continental crust during Pre -Jurassic / in early Jurassic times.Clastics and volcano-clastics which had been metamorphosed to blueschist were also deposited in the Triassic sea thenthay were thrusted over continental crust during Late Triassic / very Early Liassic times.The area which had the stable shelf character particularly during Late Triassic time were again effected by thetensional system towards the Early Cretaceous time and thick clastic rocks were deposited in the outcomingdepressions.