An arbitrary chronologic arrangement or sequence of geologic events, used as a measure of the relative or absolute duration or age of any part of geologic time, and usually presented in the form of a chart showing the names of the various rock-stratigraphic, time-stratigraphic, or geologic-time units, as currently understood; e.g., the geologic time scales published by Harland et al. (1982), Odin (1982), Palmer (1983), and Salvador (1985).