Type of biozone in biostratigraphy
Paracme, as used in biostratigraphy, is a term that describes the interval of temporary disappearance or absence of a taxon. It defines the interval between when a taxon temporarily disappears and when it reappears in biostratigraphical observation. Paracme Base "PB" (lowest occurrence) is used to denote the start of the disappearance, and Paracme Top "PT" (highest occurrence) denotes the reappearance of the taxon. 
Notable examples.
There are several instances where paracme have been reported in nannoplankton and sometimes used as a biostratigraphy marker.
References.
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