The geochemistry of marine sediments involves the study of the chemical composition and processes affecting the sediments found on the ocean floor. These sediments are derived from various sources, including terrestrial material transported by rivers, biogenic particles from marine organisms, volcanic ash, and extraterrestrial particles. The composition of marine sediments is influenced by factors such as the productivity of marine life, ocean currents, and climatic conditions. Marine sediments are categorized into terrigenous, biogenic, hydrogenous, and cosmogenic sediments. Terrigenous sediments are primarily composed of clays and silts derived from land erosion, while biogenic sediments consist mainly of calcium carbonate and silica from the remains of marine organisms like foraminifera and diatoms. Hydrogenous sediments form from the precipitation of dissolved minerals in seawater, such as manganese nodules. Cosmogenic sediments, though minor in quantity, originate from space. Chemical interactions between these sediments and seawater play a crucial role in the global cycling of elements such as carbon, nitrogen, and sulfur. Diagenetic processes, occurring within the sediment layers, further alter the original composition through microbial activity, chemical reactions, and physical changes. This book is a valuable compilation of topics, ranging from the basic to the most complex advancements in the field of geochemistry. This book presents the complex subject of geochemistry in the most comprehensible and easy to understand language. Students, researchers, experts and all associated with this subject will benefit alike from this book.