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Geochronologic and Chronostratigraphic Nomenclature to be used in AAPG Publications

* Geochronologic modifiers are in regular type while chronostratigraphic modifiers are in italics.

Formal Informal Formal Informal

Cenozoic

early, lower, middle, middle, late, upper

Paleozoic

early, lower, middle, middle, late, upper

Quaternary

Holocene (Recent)

Pleistocene

Tertiary

(Neogene + Paleogene)

Pliocene

Miocene

Oligocene

Eocene

Paleocene

early, lower, late, upper

early, lower, late, upper

early, lower, late, upper

 

early, lower, late, upper

early, lower, late, upper

early, lower, middle, middle, late, upper

early, lower, late, upper

early, lower, middle, middle, late, upper

early, lower, late, upper

Permian

  • Late, Upper
  • Early, Lower

Carboniferous

  • Pennsylvanian or Late, Upper Carboniferous
  • Mississippian or Early, Lower Carboniferous

Devonian

  • Late, Upper
  • Middle, Middle
  • Early, Lower

Silurian

  • Late, Upper
  • Early, Lower

Ordovician

  • Late, Upper
  • Middle, Middle
  • Early, Lower

Cambrian

  • Late, Upper
  • Middle, Middle
  • Early, Lower

middle, middle

 

middle, middle

 

 

 

 

 

 

 

middle, middle **

Mesozoic

early, lower, middle, middle, late, upper

Precambrian

early, lower, middle, middle, late, upper

Cretaceous

  • Late, Upper
  • Early, Lower

Jurassic

  • Late, Upper
  • Middle, Middle
  • Early, Lower

Triassic

  • Late, Upper
  • Middle, Middle
  • Early, Lower

middle, middle

Proterozoic

  • Late
  • Middle
  • Early

Archean

  • Late
  • Middle
  • Early
  • upper, Precambrian Z and VI
  • middle, Precambrian Y and V
  • lower, Precambrian X and IV
  • upper, Precambrian W and III
  • middle, Precambrian V and II
  • lower, Precambrian U and I ***

* For tables of generally accepted formal Age/Stage names, see one or more of the following: Salvador (1985); Palmer (1983); Harland et al. (1982); Odin (1982a, b; 1984). These references include isotopic ages of Age/Stage boundaries. They do not, however, agree on all Age/Stage names or numerical ages of boundaries.

** The four references cited above formally recognize a two-fold subdivision of the Silurian. The US Geological Survey formally recognizes three (Luttrell et al. 1986).

*** Regular, or Roman numerals are widely used for Precambrian subdivisions in the USSR.

Reproduced from The Journal of Sedimentary Petrology, Vol. 57, No. 2, March 1987, p. 363-372 by permission of The Society of Economic Paleontologists and Mineralogists.