On the other hand, the set of unconformities spanning the base of the Phanerozoic (i.e., definition 1) are in a sense synchronous by nature, as is consequently, to some extent, the broader phenomenon ...
R. M. Flowers, F. A. Macdonald, C. S. Siddoway, R. Havranek, Diachronous development of Great Unconformities before Neoproterozoic Snowball Earth. Proc. Natl. Acad ...