4.6 Polarity-chronological units
4.6.1 General properties and rules
A polarity-chronological unit is a division of geological time that denotes the time interval represented by a polarity-chronostratigraphical unit (Section 4.5).
The polarity chron (polaritetskronen) is the fundamental polarity-chronological unit. It designates the time span of a polarity chronozone. The hierarchy of polarity-chronological units, in decreasing order of rank, is polarity superchron (polaritetsoverkron), polarity chron and polarity subchron (polaritetsunderkron) (Table 1).
Formal names of polarity-chronological units are identical with those of corresponding polarity-chronostratigraphical units, except that chron, superchron and subchron replace chronozone, superchronozone and subchronozone, respectively.
Key reference: NACSN (1983).
