Several basins are nested on top of one another in the Marmara Region as a result of complex series of tectonic processes. These processes are related to the evolution of the Thrace Basin, North Anatolian Shear Zone and the Sea of Marmara. The Thrace Basin evolved during the early to medial Eocene (Lutetian) as a forearc basin above the northward subducting Intra-Pontide Ocean. The basin was largely deformed and eroded during the Lutetian when the Intra-Pontide Ocean closed. Following this closure, the basin turned into a remnant forearc and continued accumulating sediments with calc-alkalic volcanic rocks. When the subducting slab finally detached and fell at the end of the Oligocene, it underwent a basin-wide deformation and erosion in the early Miocene. From medial Miocene onward, a dextral shear zone superimposed the Thrace Basin. Evolution of the shear zone began in the medial Miocene and still continues with various tectonic structures, representing the pre-peak, peak, post-peak and pre-residual stages. The Sea of Marmara probably formed during the Pliocene to Pleistocene along a variety of Riedel and P-shears of the post-peak and pre-residual structure stages.