Gelasian
Earliest Quaternary age (2.58–1.80 Ma); originally the uppermost Pliocene stage.
Language and route: International scientific formation from Italian locality Gela (Sicily). International scientific formation from Italian locality Gela (Sicily). Italian place-name, deeper derivation not necessary for geological naming.
Literal gloss: of Gela
The name and its history
Domenico Rio, Rodolfo Sprovieri & Enrico Di Stefano · 1994 proposal; 1998 international ratification; 2009 reassignment
- What does the word literally mean?
- of Gela
- What did the original author mean?
- In 1994 the proposers specifically called the Gelasian a new Upper Pliocene stage; its name marked the Monte San Nicola stratotype near Gela, rather than denoting the beginning of the ice age.
- Why was the name needed?
- They sought a stable, globally correlatable subdivision above the Piacenzian to organise late Pliocene marine sedimentary successions and their climate chronology.
- What evidence supported the original concept?
- The proposal used an astronomically calibrated sapropel level, marine microfossil correlation and the nearby Gauss–Matuyama geomagnetic polarity transition.
- How has geology changed the concept?
- In 2009 the IUGS lowered the base of the Quaternary and Pleistocene to the Gelasian GSSP; an originally Pliocene stage consequently became the earliest Pleistocene stage without moving its lower boundary.
Further historical context
In 1994 the proposers specifically called the Gelasian a new Upper Pliocene stage; its name marked the Monte San Nicola stratotype near Gela, rather than denoting the beginning of the ice age.
They sought a stable, globally correlatable subdivision above the Piacenzian to organise late Pliocene marine sedimentary successions and their climate chronology.
The proposal used an astronomically calibrated sapropel level, marine microfossil correlation and the nearby Gauss–Matuyama geomagnetic polarity transition.
In 2009 the IUGS lowered the base of the Quaternary and Pleistocene to the Gelasian GSSP; an originally Pliocene stage consequently became the earliest Pleistocene stage without moving its lower boundary.
Editorial qualification
The 1994 coauthors differ from the 1998 ratification paper; neither date should be substituted for 2009 reassignment.
Related names
Quaternary · Pleistocene · Pliocene · Piacenzian · Calabrian
Sources
- ICS, International Chronostratigraphic Chart v2026/06 — Governing classification, chronological sequence and numerical reference ages; not naming priority
- Rio, Sprovieri & Di Stefano (1994), The Gelasian Stage: a proposal of a new chronostratigraphic unit of the Pliocene Series — Original 1994 proposal: explicitly an Upper Pliocene subdivision
- Rio et al. (1998), The Gelasian Stage (Upper Pliocene), Episodes 21:82–87 — Original global acceptance while still assigned to Pliocene
- ICS, Gelasian GSSP — Monte San Nicola GSSP and IUGS 29 June 2009 boundary transfer
- ICS Subcommission on Quaternary Stratigraphy, Major divisions — Institutional history of Quaternary stages, GSSPs, and reassignment of the Gelasian
- ICS, International Stratigraphic Guide: Chronostratigraphic Units — Stage/age, series/epoch and subseries/subepoch distinctions