Soft-particle conglomerates contain pebbles, cobbles, and even large boulders of clay, peat, or other materials which were more or less plastic at the time of deposition. A Tertiary example in Alabama and a Pennsylvanian example in Arkansas are cited. A study of modern coasts reveals that rounded boulders of clay and peat are produced along the seaward edge of the chenier plain. Although other mechanisms are available to account for such conglomerates, it is thought that most of the lithified examples represent coastal deposits. Beachrock is a member of the same class of sediments.