Abstract: The fragmental volcanic rocks of Seben region (Bolu SE Turkey) are typified by epiclastics in UpperCretaceous, while they are characterized by pyroclastics and autoclastics in Miocene. Epiclastics are well bedded andusually made of crystal and vitric tuffs, but occasional levels of lithic tuffs are also encountered. All of these components were rapidly eroded and transported away from volcanic areas.Pyroclastics consist of local vulcanien breccias and widespread cold pyrociastic flow breccias as well as agglomerates. These pyrociastic succession is overlain by autoclastic breccias. All of fragments have andesitic-basaltic features. The volcanosediments of Miocene in the north-northeast of Seben essentially have been derived from volcanic ventswith phreatic eruptions.