As so defined the hemipelagic deposits are those which occur in general on the slope from the continental shelves to the ocean depths and also in the deep basins of enclosed and fringing seas.
Hemipelagic deposits are a mixture of deposits of terrigenous and pelagic origin.
These peculiarities, combined with the striking absence of mineral constituents, distinguish the eupelagic globigerina ooze from the hemipelagic calcareous mud.
Secondary products, such as glauconite, phosphatic concretions and manganese nodules, occur though less frequently than in the hemipelagic sediments.
Geologists are agreed that littoral and hemipelagic deposits similar to those now forming are to be found in all geological systems, but the existence in the rocks of eupelagic deposits and especially of the abysmal red clay, though viewed by some as probable, is totally denied by others.