The modern Niger delta exemplifies a type of delta in which sand as well as mud is supplied to a receiving water body of high energy. The depositional environments, and corresponding sedimentary facies, are distributed concentrically within the deltaic region. The deltaic plain is divisible into the floodplain (upper and lower), tidal swamp, and beach-barrier environments. The depositional environments present in the submerged part of the delta are: river-mouth bars, delta-front platform, prodelta slope, and open shelf. There are also in the submerged part of the delta large areas where littoral and subtidal sands due to the Flandrian transgression are still exposed at the surface of sedimentation. The deltaic deposits decrease horizontally in grain size from the floodplain to the open shelf but vertically increase in coarseness from the silty clays of the open shelf to the predominantly fine- to medium-grained sands of the floodplain. This volume was based on a symposium, Deltaic Sedimentation, which was held at the AAPG/SEPM Annual Meeting in New Orleans, Louisiana on April 1965. Many geologists have become involved in studies of deltaic sediments and sedimentation processes. Some of the papers in this volume are based on detailed local studies of modern deltaic sedimentary sequences, on processes of deposition, and on physical and biological characteristics of the deltaic environments.