G-42 Precambrian rocks are among the oldest rocks that tell the history of the earth. The outcrops of these rocks, which belong to at least 550 million years ago and are called the Yedigöller formation in the region, are quite limited. The metagranites that can be seen around Ataköy Forest Depot are metamorphic rocks that have undergone metamorphism and deformation in various stages. Metamorphism is the name given to the change of the composition or structure of a rock by heat, pressure or other natural factors. The name metagranite is used to express that granitic rocks have undergone metamorphism.

Metagranites and metamorphic tectonic units form the basis of the Istanbul-Zonguldak zone. It is covered by Lower Ordovician-Carboniferous sedimentary rocks. Age findings obtained from metamorphic rocks indicate 570-590 million years ago, and these rocks show that different tectonic units collided during the formation of the Rodinian supercontinent. This event corresponds to the Pan-African orogeny.