Since 1980 a considerable amount of scientific research dealing with geochemical processes in marine sediments has been carried out. This textbook summarizes the state-of-the-art in this field of research providing a complete representation of the subject and including the most recent findings. The topics covered include the examination of sedimentological and physical properties of the sedimentary solid phase. A new chapter describes properties, occurrence and formation of gas hydrates in marine sediments. The textbook ends with a chapter on model conceptions and computer models to quantify processes of early diagenesis.