Characteristics of Clastic Sediment(2) a gravel is subdivided into Boulder gravel >256mm Cobble gravel 64 to 256mm Pebble gravel 64 to 2mmCharacteristics of Clastic Sediment (2) ◼ Gravel is subdivided into: ◼ Boulder gravel >256mm ◼ Cobble gravel 64 to 256mm ◼ Pebble gravel 64 to 2mm