Figure F4. A. Textural classification scheme for siliciclastic sediments modified from Shepard (1954) by subdivision of the central triangular field into muddy sand and sandy mud; the term "mud" is used here for a mixture of silt and clay (Shipboard Scientific Party, 1995). The sand-, silt-, and clay-sized fractions are defined using the Wentworth (1922) grade scale. Symbols used on the Shepard triangle are the same as shown in Figure F3. B. Classification of sediments composed of mixtures of biogenic and siliciclastic components. In this scheme the names shown for microfossil components and the siliciclastic fraction are examples only (i.e., placeholders), and can be replaced by any valid textural name (for siliciclastic fraction) or microfossil name.