4.7.3 Phase (Fase)
4.7.3.1 Phase is the diachronous unit that has formal rank next below episode and next above span. When phase is used formally, it must refer to one of several similar, prominent events that together constitute a major event with the rank of episode (Fig. 31). Phases in an ice-age episode may, for example, be represented by two or more "stadial" moraine formations and intermediate "interstadial" water-deposited sediments. When used informally, the word "phase" should retain a corresponding meaning of relative time.