zone-fossilhttp://www.oed.com/dictionary/zone-fossil_n%3Ftab%3Dmeaning_and_usezone fossil, n.
First published 1921; not fully revised

zone fossilnoun

Geology.
  1. 1904–
    A fossil characteristic of a particular zone or belt of strata.
    1. 1904
      The study..of strata characterised by the dominance of a zone-fossil forms zonal geology.
      Edinburgh Review January 219
    2. 1969
      It may be possible to recognize a zone without actually finding a specimen of the zone fossil itself if other highly characteristic species are found.
      G. M. Bennison & A. E. Wright, Geological History of British Isles ii. 23
    3. 1975
      Evolution needed the temporal and biological continuum which Lyell's theory made possible. And from this came the concept of the ‘zone fossil’.
      J. G. Evans, Environment of Early Man in British Isles iii. 69

Originally published as part of the entry for zone, n.

zone, n. was first published in 1921; not fully revised.