Abstract: Manganese nodules in the dölostone and radiolarian brown claystone in the Konak Formation of KoçaliComplex Upper Jurassic-Lower Cretaceous in age had been developed by early diagenetic processes. The replacement of silicic tests by Mn and other transition heavy metals such as Cu, Ni, Ba is the main mechanism of the nodule development. Both manganese nodules and associated manganese mineralization was effected by late diagenetic processes. The proceses resulted in the dissolution and migration of elements such as Cu, Ni, Mn, Si and addition of the elements such as Ca, Mg, Si. Thus, dolomite manganocalcite, calcite, quartz and pyrolusite veinlets formed as late diagenetic mineral assamblages. Hydrogenetic manganese nodules was not formed at the sediment sea water interface owing to oceanic bottom currents and episodic fluctuations of Mn in the sea water. Another reason for the absance of formationhydrogenous manganese nodules could be high sedimentation rate which indicates an enverionment close to active plate margin.